Define Newton's first law of motion .

A body remains at rest or moves with constant velocity unless acted on by a resultant force .

Define terminal velocity .

The maximum, constant velocity reached when the forces acting in the direction of motion are balanced by the forces opposing motion.

Give two ways a car designer could reduce the forces opposing motion, to increase the car's terminal velocity.

Any two from: Use tyres with less grip Make the car body more streamlined Reduce friction in the engine (better oil) Reduce friction in the wheel bearings (smoother surfaces/lubricants)

A skydiver reaches terminal velocity when the forces in the direction of motion are .......... by the forces opposing motion.

A skydiver reaches terminal velocity when the forces in the direction of motion are balanced by the forces opposing motion.

True or False? If the resultant force on an object is zero, the object must be at rest.

False. A zero resultant force means the object is at rest or moving with constant velocity — this is Newton's first law .

The measure of the amount of matter in an object; the property that resists change in motion. SI unit: kilogram (kg) .

In .......... , the only force acting on a falling object is its weight, so drag forces are ignored.

In freefall , the only force acting on a falling object is its weight, so drag forces are ignored.

True or False? A heavier object falls faster than a lighter object in freefall.

False. In freefall , all objects accelerate at the same rate, g , regardless of mass, since weight is proportional to mass.

In the electromagnet and timer method for determining g , what are the independent and dependent variables?

Independent variable: height, h Dependent variable: time, t

Define the main systematic error in the electromagnet freefall experiment.

Residual magnetism remaining after the electromagnet is switched off, which causes the recorded time, t , to be longer than it should be .

In the ramp and trolley experiment, a graph of velocity, v , against time, t , is plotted. What do the gradient and y-intercept represent?

Gradient = acceleration due to gravity Y-intercept = initial velocity, u

In freefall experiments, each height, h , is repeated at least three to five times and an average value of t is calculated to reduce .......... errors.

In freefall experiments, each height, h , is repeated at least three to five times and an average value of t is calculated to reduce random errors.

True or False? The cushion placed under the falling ball bearing is used to reduce random errors in the timing.

False. The cushion is a safety measure, to stop the ball bearing rolling away or damaging the surface — it does not affect the accuracy of the timing.

Define Newton's third law of motion .

Whenever two bodies interact, the forces they exert on each other are equal in size , act in opposite directions , and are of the same type .

State the two conditions needed for two forces to form a genuine Newton's third law pair.

The forces must be equal in magnitude and opposite in direction The forces must be the same type , acting on two different objects

A trolley (object A) exerts a force of 12 N on a wall (object B) during a collision. What force does the wall exert on the trolley, and why?

12 N , equal in magnitude, opposite in direction, and of the same type (contact force) — by Newton's third law.

A Newton's third law force pair consists of two forces of the .......... type, acting on two different objects.

A Newton's third law force pair consists of two forces of the same type, acting on two different objects.

True or False? The forces in a Newton's third law pair always act on the same object.

False. Newton's third law force pairs always act on two different objects — forces on the same object are considered under Newton's first law .

A tennis ball (small mass, high speed) and a brick (large mass, low speed) have the same momentum. What does this tell you about the force each exerts on impact?

They would exert a similar force on impact, since their momentum — and therefore rate of change of momentum — is the same (for a given collision time).

Momentum is a .......... quantity, meaning it has both magnitude and direction.

Momentum is a vector quantity, meaning it has both magnitude and direction.

True or False? An object moving to the left always has negative momentum.

False. The sign of momentum depends on which direction is chosen as positive — an object moving left only has negative momentum if right is defined as the positive direction.

Define the principle of conservation of momentum .

In a closed system , with no external forces, the total momentum before an event is equal to the total momentum after the event.

In a closed system, momentum is conserved because colliding objects exert .......... and opposite forces on each other.

In a closed system, momentum is conserved because colliding objects exert equal and opposite forces on each other.

True or False? If two objects moving towards each other have equal and opposite momenta, the total momentum of the system is zero.

True. Since momentum is a vector quantity, momenta in opposite directions cancel, giving a total system momentum of zero .

International A Level (IAL)PhysicsEdexcelFlashcards1. Mechanics & MaterialsForces & Momentum

Forces & Momentum (Edexcel International A Level (IAL) Physics): Flashcards

Exam code: YPH11

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Define Newton's first law of motion.

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Cards in this collection (38)

Define Newton's first law of motion.
A body remains at rest or moves with constant velocity unless acted on by a resultant force.
Define terminal velocity.
The maximum, constant velocity reached when the forces acting in the direction of motion are balanced by the forces opposing motion.
State Newton's second law of motion.
The acceleration of an object of constant mass is directly proportional to the resultant force acting on it: $Σ F = m a$
An object of mass 750 g accelerates at 11 m s^-2. Calculate the resultant force acting on it.
$Σ F = m a = 0.750 \times 11$
ΣF = 8.3 N
Give two ways a car designer could reduce the forces opposing motion, to increase the car's terminal velocity.
Any two from:
- Use tyres with less grip
- Make the car body more streamlined
- Reduce friction in the engine (better oil)
- Reduce friction in the wheel bearings (smoother surfaces/lubricants)
A skydiver reaches terminal velocity when the forces in the direction of motion are .......... by the forces opposing motion.
A skydiver reaches terminal velocity when the forces in the direction of motion are balanced by the forces opposing motion.
True or False?
If the resultant force on an object is zero, the object must be at rest.
False.
A zero resultant force means the object is at rest or moving with constant velocity — this is Newton's first law.
Define mass.
The measure of the amount of matter in an object; the property that resists change in motion. SI unit: kilogram (kg).
Define gravitational field strength.
The force per unit mass acting on an object in a gravitational field: $g = \frac{F}{m}$ , measured in N kg^-1.
State the equation linking weight, mass and gravitational field strength.
$W = m g$
What is the average gravitational field strength at the Earth's surface?
9.81 N kg^-1
Why do all objects in freefall (with no drag) accelerate at the same rate, regardless of their mass?
Weight is proportional to mass ( $W = m g$ ), so the acceleration $\frac{W}{m} = g$ is the same for every mass.
In .........., the only force acting on a falling object is its weight, so drag forces are ignored.
In freefall, the only force acting on a falling object is its weight, so drag forces are ignored.
True or False?
A heavier object falls faster than a lighter object in freefall.
False.
In freefall, all objects accelerate at the same rate, g, regardless of mass, since weight is proportional to mass.
In the electromagnet and timer method for determining g, what are the independent and dependent variables?
Independent variable: height, h
Dependent variable: time, t
A graph of height, h, against t² is plotted for the electromagnet freefall experiment. What does the gradient represent?
Gradient = $\frac{1}{2} g$ , since $h = \frac{1}{2} g t^{2}$ (as u = 0).
In the card and light gate method, a graph of v² is plotted against 2h. What does the gradient equal?
The gradient equals g, since $v^{2} = 2 g h$ (as u = 0).
Define the main systematic error in the electromagnet freefall experiment.
Residual magnetism remaining after the electromagnet is switched off, which causes the recorded time, t, to be longer than it should be.
In the ramp and trolley experiment, a graph of velocity, v, against time, t, is plotted. What do the gradient and y-intercept represent?
Gradient = acceleration due to gravity
Y-intercept = initial velocity, u
In freefall experiments, each height, h, is repeated at least three to five times and an average value of t is calculated to reduce .......... errors.
In freefall experiments, each height, h, is repeated at least three to five times and an average value of t is calculated to reduce random errors.
True or False?
The cushion placed under the falling ball bearing is used to reduce random errors in the timing.
False.
The cushion is a safety measure, to stop the ball bearing rolling away or damaging the surface — it does not affect the accuracy of the timing.
Define Newton's third law of motion.
Whenever two bodies interact, the forces they exert on each other are equal in size, act in opposite directions, and are of the same type.
State the two conditions needed for two forces to form a genuine Newton's third law pair.
- The forces must be equal in magnitude and opposite in direction
- The forces must be the same type, acting on two different objects
A trolley (object A) exerts a force of 12 N on a wall (object B) during a collision. What force does the wall exert on the trolley, and why?
12 N, equal in magnitude, opposite in direction, and of the same type (contact force) — by Newton's third law.
A Newton's third law force pair consists of two forces of the .......... type, acting on two different objects.
A Newton's third law force pair consists of two forces of the same type, acting on two different objects.
True or False?
The forces in a Newton's third law pair always act on the same object.
False.
Newton's third law force pairs always act on two different objects — forces on the same object are considered under Newton's first law.
Define linear momentum.
The product of an object's mass and velocity: $p = m v$ . It is a vector quantity with SI unit kg m s^-1.
State the equation for linear momentum, including the units of each quantity.
$p = m v$
p in kg m s^-1, m in kg, v in m s^-1
A ball has a mass of 150 g and a velocity of 20 m s^-1. Calculate its momentum.
$m = 150 g = 0.150 kg$
$p = m v = 0.150 \times 20$
p = 3.0 kg m s^-1
A tennis ball (small mass, high speed) and a brick (large mass, low speed) have the same momentum. What does this tell you about the force each exerts on impact?
They would exert a similar force on impact, since their momentum — and therefore rate of change of momentum — is the same (for a given collision time).
Momentum is a .......... quantity, meaning it has both magnitude and direction.
Momentum is a vector quantity, meaning it has both magnitude and direction.
True or False?
An object moving to the left always has negative momentum.
False.
The sign of momentum depends on which direction is chosen as positive — an object moving left only has negative momentum if right is defined as the positive direction.
Define the principle of conservation of momentum.
In a closed system, with no external forces, the total momentum before an event is equal to the total momentum after the event.
Trolley A (0.80 kg) travelling at 3.0 m s^-1 collides head-on with a stationary trolley B (twice the mass of A) and they stick together. Calculate their common velocity after the collision.
$m_{A} u_{A} = (m_{A} + m_{B}) v$
$0.80 \times 3.0 = (0.80 + 1.60) v$
v = 1.0 m s^-1
When trolley A exerts a force on trolley B during a collision, what force does trolley B exert on trolley A?
An equal force in the opposite direction, $F_{B - A} = - F_{A - B}$ , by Newton's third law.
Two trolleys of unequal mass collide and exert equal and opposite forces on each other. Do they have equal accelerations? Explain.
No. Since $a = \frac{F}{m}$ , the trolley with the smaller mass has the greater acceleration, even though the force on each is equal in magnitude.
In a closed system, momentum is conserved because colliding objects exert .......... and opposite forces on each other.
In a closed system, momentum is conserved because colliding objects exert equal and opposite forces on each other.
True or False?
If two objects moving towards each other have equal and opposite momenta, the total momentum of the system is zero.
True.
Since momentum is a vector quantity, momenta in opposite directions cancel, giving a total system momentum of zero.

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