A force is a push or pull that arises from the interaction between objects.

State the three possible effects a force can have on an object.

A force can change an object's speed , direction , or shape .

Explain why drag force and air resistance are both types of friction .

Drag force opposes the motion of an object moving through a fluid (a liquid or a gas). Air resistance is a specific type of drag that occurs when an object moves through air . Both oppose motion in the same way as friction between solid surfaces.

The reaction force exerted by a surface on an object resting on it acts at ______ to the surface.

The reaction force exerted by a surface on an object resting on it acts at right angles to the surface.

True or False? Upthrust is a downward-acting force exerted by a fluid on a submerged object.

False. Upthrust is an upward-acting push force exerted by a fluid on an object that is fully or partially submerged in it.

Tension is the force that acts across the length of an object, such as a rope or spring, when a pull force is exerted on each end of it.

How do electrostatic forces and magnetic forces each depend on the charges or poles involved?

For electrostatic forces, like charges repel and opposite charges attract . For magnetic forces, like poles repel and opposite poles attract .

Define scalar quantity.

A scalar quantity has magnitude but no direction, for example mass.

Define vector quantity.

A vector quantity has both magnitude and direction , for example weight.

What is the difference between distance and displacement ?

Distance is the total length of the path travelled, regardless of direction (a scalar). Displacement is the length and direction of a straight line from the starting point to the finishing point (a vector).

Can an object have a constant speed but a changing velocity ? Explain.

Yes. Velocity includes direction, so an object moving at a constant speed but continuously changing direction has a changing velocity, even though its speed stays the same.

When a force is represented by an arrow, the ______ of the arrow shows the magnitude of the force, and the ______ of the arrow shows its direction.

When a force is represented by an arrow, the length of the arrow shows the magnitude of the force, and the direction of the arrow shows its direction.

True or False? Energy is a vector quantity.

False. Energy is a scalar quantity — it has magnitude only, with no associated direction.

Name three vector quantities that have no scalar counterpart.

Force , acceleration , and momentum are all vector quantities with no corresponding scalar equivalent.

Define resultant force .

A resultant force is the single force that describes the combined effect of all the forces acting on an object, determining both its magnitude and direction.

Friction is a force which opposes the motion of an object, occurring when two (or more) surfaces rub against each other.

How do you calculate the resultant force when two forces act in opposite directions on an object?

Subtract the smaller force from the larger force. The resultant force acts in the direction of the larger force.

When stating a resultant force, you should always give both its ______ and its ______ .

When stating a resultant force, you should always give both its magnitude and its direction .

True or False? Friction always acts in the same direction as an object's motion.

False. Friction always acts in the opposite direction to an object's motion, opposing it.

At a molecular level, why does friction occur between two surfaces in contact?

Both surfaces contain microscopic imperfections (they are not perfectly smooth), and these imperfections push against each other as the surfaces rub together.

Define balanced forces .

Balanced forces combine so that they cancel out completely, resulting in zero resultant force on an object — for example, the weight of a book balanced by the normal force from a table.

Define unbalanced forces .

Unbalanced forces combine so that they do not cancel out completely, resulting in a resultant force acting on the object.

In a tug-of-war, person A pulls with 80 N to the left and person B pulls with 100 N to the right. What is the resultant force?

The forces are unbalanced . Resultant force = 100 − 80 = 20 N to the right .

A resultant force acting on an object can cause it to ______ , ______ , or ______ .

A resultant force acting on an object can cause it to speed up , slow down , or change direction .

True or False? If the forces acting on an object are balanced, the object accelerates.

False. When forces are balanced , the resultant force is zero , so the object does not accelerate — it continues at constant velocity, or remains at rest.

In the equation F = ma , what does a negative value of the resultant force indicate?

A negative resultant force acts in the opposite direction to the object's motion, causing it to decelerate (slow down).

Weight is the force experienced by an object with mass when placed in a gravitational field .

Why is mass a scalar quantity but weight a vector quantity?

Mass is a measure of the amount of matter in an object and has magnitude only. Weight is a force, so it has both magnitude and direction .

On Earth, the gravitational field strength is ______ , and the acceleration of freefall is ______ .

On Earth, the gravitational field strength is 10 N/kg , and the acceleration of freefall is 10 m/s^2^ .

An astronaut has a mass of 40 kg. Earth's gravitational field strength is 10 N/kg and the Moon's is 2 N/kg. Calculate her weight on each.

Weight on Earth = 40 × 10 = 400 N . Weight on the Moon = 40 × 2 = 80 N .

True or False? An object's mass changes depending on which planet it is on.

False. Mass stays the same wherever an object is; it is the object's weight that changes, because gravitational field strength differs between planets.

Define stopping distance .

Stopping distance is the total distance travelled during the time it takes a car to stop in an emergency: stopping distance = thinking distance + braking distance .

Define thinking distance .

Thinking distance is the distance travelled in the time it takes the driver to react to an emergency and prepare to stop.

Define braking distance .

Braking distance is the distance travelled under the braking force, once the brakes have been applied.

What is reaction time ?

Reaction time is a measure of how much time passes between seeing something and reacting to it. The average human reaction time is 0.25 s.

State three factors that increase a driver's reaction time , and so their thinking distance .

Tiredness , distractions (e.g. using a mobile phone, satnav, radio or a passenger) and intoxication (consumption of alcohol or drugs).

How do wet or icy road conditions affect a vehicle's braking distance ?

They make the brakes less effective , so the vehicle travels further before it stops (braking distance increases).

For a given braking force, the greater the speed of a vehicle, the the stopping distance.

For a given braking force, the greater the speed of a vehicle, the greater the stopping distance.

True or False? Increasing a vehicle's mass decreases its braking distance.

False. The more massive the vehicle, the more distance it travels as it comes to a stop, so braking distance increases with mass.

Define terminal velocity .

Terminal velocity is the fastest, constant speed a falling object reaches once the upward and downward forces acting on it are balanced, so the resultant force is zero.

Define air resistance (drag).

Air resistance is the frictional force that opposes an object's motion through the air, caused by collisions with air particles. It increases as the object's speed increases.

Describe how the acceleration of a skydiver changes between stepping out of the plane and reaching terminal velocity.

Initially, only weight acts, so acceleration is at its maximum . As speed increases, air resistance increases, so the resultant force (and acceleration) decreases . Acceleration reaches zero once air resistance equals weight, and a constant (terminal) velocity is reached.

Why does air resistance increase as a falling object's speed increases?

The object collides with a greater number of air particles per second as it moves faster, increasing the frictional force acting against it.

Terminal velocity is reached when the resultant force on a falling object becomes .

Terminal velocity is reached when the resultant force on a falling object becomes zero .

True or False? At terminal velocity, the force of air resistance is greater than the force of weight.

False. At terminal velocity, air resistance is equal to weight, so the forces are balanced and the resultant force is zero.

In the core practical investigating force and extension, what is the independent variable ?

Force , F (applied by adding masses to the hanger).

What piece of equipment is used with a spring or rubber band to take an accurate reading of extension, and why?

A pointer (also called a fiducial marker ), because it allows the extension to be read from the ruler accurately.

Give two safety precautions taken during the force–extension practical.

Wear goggles in case the spring, rubber band or wire snaps. Stand up during the experiment with no feet directly under the masses. (Also acceptable: place a mat below the masses; use a G-clamp to secure the clamp stand.)

IGCSEPhysicsEdexcelPhysics (Modular)Unit 1Flashcards1. Forces & MotionForces, Movement & Changing Shape

Forces, Movement & Changing Shape (Edexcel IGCSE Physics (Modular): Unit 1): Flashcards

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FrontTypes of Forces
Define force.

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Cards in this collection (66)

Define force.
A force is a push or pull that arises from the interaction between objects.
State the three possible effects a force can have on an object.
A force can change an object's speed, direction, or shape.
Explain why drag force and air resistance are both types of friction.
Drag force opposes the motion of an object moving through a fluid (a liquid or a gas). Air resistance is a specific type of drag that occurs when an object moves through air. Both oppose motion in the same way as friction between solid surfaces.
The reaction force exerted by a surface on an object resting on it acts at ______ to the surface.
The reaction force exerted by a surface on an object resting on it acts at right angles to the surface.
True or False?
Upthrust is a downward-acting force exerted by a fluid on a submerged object.
False.
Upthrust is an upward-acting push force exerted by a fluid on an object that is fully or partially submerged in it.
Define tension.
Tension is the force that acts across the length of an object, such as a rope or spring, when a pull force is exerted on each end of it.
How do electrostatic forces and magnetic forces each depend on the charges or poles involved?
For electrostatic forces, like charges repel and opposite charges attract. For magnetic forces, like poles repel and opposite poles attract.
Define scalar quantity.
A scalar quantity has magnitude but no direction, for example mass.
Define vector quantity.
A vector quantity has both magnitude and direction, for example weight.
What is the difference between distance and displacement?
Distance is the total length of the path travelled, regardless of direction (a scalar). Displacement is the length and direction of a straight line from the starting point to the finishing point (a vector).
Can an object have a constant speed but a changing velocity? Explain.
Yes. Velocity includes direction, so an object moving at a constant speed but continuously changing direction has a changing velocity, even though its speed stays the same.
When a force is represented by an arrow, the ______ of the arrow shows the magnitude of the force, and the ______ of the arrow shows its direction.
When a force is represented by an arrow, the length of the arrow shows the magnitude of the force, and the direction of the arrow shows its direction.
True or False?
Energy is a vector quantity.
False.
Energy is a scalar quantity — it has magnitude only, with no associated direction.
Name three vector quantities that have no scalar counterpart.
Force, acceleration, and momentum are all vector quantities with no corresponding scalar equivalent.
Define resultant force.
A resultant force is the single force that describes the combined effect of all the forces acting on an object, determining both its magnitude and direction.
Define friction.
Friction is a force which opposes the motion of an object, occurring when two (or more) surfaces rub against each other.
How do you calculate the resultant force when two forces act in opposite directions on an object?
Subtract the smaller force from the larger force. The resultant force acts in the direction of the larger force.
How do you calculate the resultant force when two forces act in the same direction on an object?
Add the two forces together.
When stating a resultant force, you should always give both its ______ and its ______.
When stating a resultant force, you should always give both its magnitude and its direction.
True or False?
Friction always acts in the same direction as an object's motion.
False.
Friction always acts in the opposite direction to an object's motion, opposing it.
At a molecular level, why does friction occur between two surfaces in contact?
Both surfaces contain microscopic imperfections (they are not perfectly smooth), and these imperfections push against each other as the surfaces rub together.
Define balanced forces.
Balanced forces combine so that they cancel out completely, resulting in zero resultant force on an object — for example, the weight of a book balanced by the normal force from a table.
Define unbalanced forces.
Unbalanced forces combine so that they do not cancel out completely, resulting in a resultant force acting on the object.
State the equation linking resultant force, mass and acceleration, and define each symbol.
$F = m a$
Where F = resultant force (N), m = mass (kg), a = acceleration (m/s²). This is also known as Newton's second law of motion.
In a tug-of-war, person A pulls with 80 N to the left and person B pulls with 100 N to the right. What is the resultant force?
The forces are unbalanced. Resultant force = 100 − 80 = 20 N to the right.
A resultant force acting on an object can cause it to ______, ______, or ______.
A resultant force acting on an object can cause it to speed up, slow down, or change direction.
True or False?
If the forces acting on an object are balanced, the object accelerates.
False.
When forces are balanced, the resultant force is zero, so the object does not accelerate — it continues at constant velocity, or remains at rest.
In the equation F = ma, what does a negative value of the resultant force indicate?
A negative resultant force acts in the opposite direction to the object's motion, causing it to decelerate (slow down).
Define weight.
Weight is the force experienced by an object with mass when placed in a gravitational field.
Define gravitational field strength.
Gravitational field strength (g) is a measure of the strength of a planet's gravitational pull, linked to weight and mass by $W = m g$ . On Earth, g = 10 N/kg.
Why is mass a scalar quantity but weight a vector quantity?
Mass is a measure of the amount of matter in an object and has magnitude only. Weight is a force, so it has both magnitude and direction.
State the equation linking weight, mass and gravitational field strength, and define each symbol.
$W = m g$
Where W = weight (N), m = mass (kg), g = gravitational field strength (N/kg).
On Earth, the gravitational field strength is ______, and the acceleration of freefall is ______.
On Earth, the gravitational field strength is 10 N/kg, and the acceleration of freefall is 10 m/s^2^.
An astronaut has a mass of 40 kg. Earth's gravitational field strength is 10 N/kg and the Moon's is 2 N/kg. Calculate her weight on each.
Weight on Earth = 40 × 10 = 400 N. Weight on the Moon = 40 × 2 = 80 N.
True or False?
An object's mass changes depending on which planet it is on.
False.
Mass stays the same wherever an object is; it is the object's weight that changes, because gravitational field strength differs between planets.
Define stopping distance.
Stopping distance is the total distance travelled during the time it takes a car to stop in an emergency: stopping distance = thinking distance + braking distance.
Define thinking distance.
Thinking distance is the distance travelled in the time it takes the driver to react to an emergency and prepare to stop.
Define braking distance.
Braking distance is the distance travelled under the braking force, once the brakes have been applied.
What is reaction time?
Reaction time is a measure of how much time passes between seeing something and reacting to it. The average human reaction time is 0.25 s.
State three factors that increase a driver's reaction time, and so their thinking distance.
Tiredness, distractions (e.g. using a mobile phone, satnav, radio or a passenger) and intoxication (consumption of alcohol or drugs).
How do wet or icy road conditions affect a vehicle's braking distance?
They make the brakes less effective, so the vehicle travels further before it stops (braking distance increases).
For a given braking force, the greater the speed of a vehicle, the the stopping distance.
For a given braking force, the greater the speed of a vehicle, the greater the stopping distance.
True or False?
Increasing a vehicle's mass decreases its braking distance.
False.
The more massive the vehicle, the more distance it travels as it comes to a stop, so braking distance increases with mass.
Define terminal velocity.
Terminal velocity is the fastest, constant speed a falling object reaches once the upward and downward forces acting on it are balanced, so the resultant force is zero.
Define air resistance (drag).
Air resistance is the frictional force that opposes an object's motion through the air, caused by collisions with air particles. It increases as the object's speed increases.
Which two forces act on a falling object?
Weight and air resistance.
Why does an object's weight stay constant as it falls?
Because $W = m g$ , and both the mass, m, and the gravitational field strength, g, remain unchanged during the fall.
Describe how the acceleration of a skydiver changes between stepping out of the plane and reaching terminal velocity.
Initially, only weight acts, so acceleration is at its maximum. As speed increases, air resistance increases, so the resultant force (and acceleration) decreases. Acceleration reaches zero once air resistance equals weight, and a constant (terminal) velocity is reached.
Why does air resistance increase as a falling object's speed increases?
The object collides with a greater number of air particles per second as it moves faster, increasing the frictional force acting against it.
Terminal velocity is reached when the resultant force on a falling object becomes .
Terminal velocity is reached when the resultant force on a falling object becomes zero.
True or False?
At terminal velocity, the force of air resistance is greater than the force of weight.
False.
At terminal velocity, air resistance is equal to weight, so the forces are balanced and the resultant force is zero.
In the core practical investigating force and extension, what is the independent variable?
Force, F (applied by adding masses to the hanger).
In the core practical investigating force and extension, what is the dependent variable?
Extension, e.
What piece of equipment is used with a spring or rubber band to take an accurate reading of extension, and why?
A pointer (also called a fiducial marker), because it allows the extension to be read from the ruler accurately.
How is the extension of a metal wire calculated in this practical?
$e = new marker reading - reference point reading$ , using a piece of tape as the marker on the wire.
How is the force applied by each mass calculated in this practical?
The force is the weight of the mass: $W = m g$ , using g = 10 N/kg. For example, a 300 g (0.3 kg) mass applies a force of 3 N.
Give two safety precautions taken during the force–extension practical.
Wear goggles in case the spring, rubber band or wire snaps. Stand up during the experiment with no feet directly under the masses. (Also acceptable: place a mat below the masses; use a G-clamp to secure the clamp stand.)
The experiment is repeated a total of times so that an average length can be calculated for each mass added.
The experiment is repeated a total of three times so that an average length can be calculated for each mass added.
True or False?
The G-clamp and wooden blocks in the metal wire experiment are used to measure the wire's extension.
False.
They are used to apply an opposing (anchoring) force at the end of the wire, holding it in place. The extension is measured using the ruler and tape marker.
Define Hooke's law.
Hooke's law states that the extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality.
Define the limit of proportionality.
The limit of proportionality is the point beyond which the relationship between force and extension is no longer directly proportional. This limit varies according to the material.
What is the difference between elastic and inelastic deformation?
Elastic deformation: the object returns to its original shape once the deforming force is removed (not permanent), e.g. rubber bands, fabrics, steel springs. Inelastic deformation: the object does not return to its original shape (permanent), e.g. plastic, clay, glass.
On a force-extension graph, what feature shows that a material obeys Hooke's law?
A straight-line (linear) region through the origin. Beyond the limit of proportionality, the graph becomes non-linear (curved).
If the force applied to a spring, within its limit of proportionality, is doubled, what happens to its extension?
The extension also doubles, since force and extension are directly proportional.
Hooke's law states that the extension of an elastic object is proportional to the force applied, up to the limit of proportionality.
Hooke's law states that the extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality.
True or False?
Glass is an example of a material that undergoes elastic deformation.
False.
Glass undergoes inelastic deformation — it does not return to its original shape once broken or permanently deformed. Rubber bands, fabrics and steel springs are examples of elastic materials.

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