Distance is the total length between two points. It is a scalar quantity (magnitude only).

Define displacement .

Displacement is the distance of an object from a fixed point in a specified direction. It is a vector quantity.

Distinguish between speed and velocity .

Speed is a scalar quantity: the total distance travelled per unit of time Velocity is a vector quantity: the rate of change of displacement of an object

Acceleration is the rate of change of .......... of an object.

Acceleration is the rate of change of velocity of an object.

How do you find the instantaneous velocity of an object at a given point on a displacement-time graph?

Draw a tangent to the curve at the required time, then calculate the gradient of that tangent.

Define average speed .

Average speed is the total distance travelled divided by the total time taken.

True or False? A distance-time graph can show negative values on the distance axis.

False. Distance is a scalar quantity, so a distance-time graph can only have positive values. Only a displacement -time graph can show negative values, since displacement is a vector.

On a velocity-time graph , what does the gradient represent, and what does the area under the graph represent?

Gradient : acceleration Area under the graph : displacement (or distance) travelled

On an acceleration-time graph , what does the area under the graph represent, and what does the gradient represent?

Area under the graph : change in velocity Gradient : this is meaningless on an acceleration-time graph

What does the gradient of a displacement-time graph represent, and what does the gradient of a velocity-time graph represent?

Displacement-time graph gradient = velocity Velocity-time graph gradient = acceleration

What does the area under a velocity-time graph represent, and what does the area under an acceleration-time graph represent?

Velocity-time graph area = displacement Acceleration-time graph area = velocity

At the highest point of a bouncing ball's motion (point A), the ball momentarily has zero .......... .

At the highest point of a bouncing ball's motion (point A), the ball momentarily has zero velocity .

At the lowest point of a bouncing ball's motion (point B), how does its velocity change?

The velocity changes instantaneously from negative to positive (the direction reverses), but the speed (magnitude) remains the same.

True or False? At the lowest point of a bouncing ball's motion (point B), the ball has zero acceleration because it is momentarily at rest.

False. The ball is only momentarily at rest at the highest point (point A). At the lowest point (point B), its velocity reverses direction almost instantaneously, which causes a momentary acceleration .

What assumption allows a bouncing ball to reach the same height on each bounce?

That there are no other forces, such as air resistance , acting on the ball.

Define the SUVAT equations .

The SUVAT equations are the equations of motion used for objects undergoing constant (uniform) acceleration.

What do the five SUVAT variables represent?

s = displacement (m) u = initial velocity (m s -1 ) v = final velocity (m s -1 ) a = acceleration (m s -2 ) t = time (s)

Which of the five SUVAT quantities is not a vector quantity?

Time , t , is not a vector. All the other quantities ( s , u , v , a ) are vector quantities and so can be positive or negative depending on direction.

If a question states that an object 'starts from rest', this means the initial velocity, u , is .......... .

If a question states that an object 'starts from rest', this means the initial velocity, u , is zero .

Under what condition are the SUVAT equations valid?

They are valid only for motion with constant (uniform) acceleration in a straight line.

True or False? When using SUVAT equations, upwards must always be taken as the positive direction.

False. It does not matter which direction is taken as positive, as long as the sign convention is applied consistently to all vector quantities throughout the problem.

Define a projectile .

A projectile is a particle moving freely (non-powered), under gravity, in a two-dimensional plane.

In projectile motion, what are the horizontal and vertical components of an initial velocity u at angle θ to the horizontal?

Horizontal component = u cos θ Vertical component = u sin θ

In projectile motion, the horizontal and vertical components of displacement, velocity and acceleration are .......... of each other.

In projectile motion, the horizontal and vertical components of displacement, velocity and acceleration are independent of each other.

For a projectile launched and landing at the same height, what fraction of the total time of flight has elapsed when it reaches maximum height?

Half of the total time of flight.

What are the horizontal velocity and horizontal acceleration of a projectile (ignoring air resistance)?

Horizontal velocity is constant Horizontal acceleration is zero

True or False? At maximum height, a projectile's horizontal velocity is zero.

False. At maximum height, the vertical velocity is zero (the projectile is momentarily at rest vertically). The horizontal velocity remains constant throughout the flight.

How does air resistance affect the range and maximum height of a projectile?

Reduces the horizontal component of velocity, decreasing the range Reduces the maximum height reached Causes a steeper gradient as the projectile falls back to the ground

What two main factors affect the motion of an object moving through a fluid?

Mass : a greater mass means a greater weight Surface area : a larger surface area means a greater air resistance

Define a drag force .

A drag force is a force that opposes the motion of an object moving through a fluid (gas or liquid), for example friction or air resistance.

What effect can a drag force never have on a moving object?

A drag force can never speed an object up or start it moving ; it can only slow an object down or keep it moving at a constant speed.

What is lift , and which Newtonian principle explains it?

Lift is an upwards force on an object moving through a fluid, perpendicular to the fluid flow It arises from Newton's third law : as, for example, an aeroplane pushes down on the air, the air exerts an equal and opposite upward reaction force on it

Drag forces convert kinetic energy into .......... and .......... .

Drag forces convert kinetic energy into heat and sound .

True or False? A drag force acting on an object stays the same size no matter how fast the object moves.

False. Drag force increases as the speed of the object increases.

Define air resistance .

Air resistance is a drag force experienced by an object as it moves through air.

Besides speed, what factors affect the air resistance (and so the maximum speed) of a moving object?

Cross-sectional area Shape Altitude Temperature Humidity

Why does a person swimming at walking pace use up far more energy than a person walking at the same pace?

Because air is around 800 times less dense than water, so air resistance has little effect at walking pace, whereas water resistance is much greater at the same speed.

How does air resistance affect a projectile's range and maximum height?

Air resistance decreases the horizontal component of velocity, which reduces both the range and the maximum height of the projectile compared to its motion without air resistance.

Define terminal velocity .

Terminal velocity is the maximum, constant velocity reached by a falling body when the drag force acting on it becomes equal to its weight.

A falling body has reached terminal velocity when the drag force acting on it is .......... to its weight.

A falling body has reached terminal velocity when the drag force acting on it is equal to its weight.

Two skydivers, A and B, jump from a plane. Skydiver A is heavier than skydiver B. Which skydiver has the higher terminal velocity, and why?

Skydiver A has the higher terminal velocity. A greater mass means a greater weight, and terminal velocity is reached when weight equals drag force, so a greater weight requires a greater speed to balance it.

True or False? When a skydiver deploys their parachute, they move upwards before continuing to fall.

False. The skydiver does not move upwards; they decelerate from their higher terminal velocity to a new, lower terminal velocity.

On a velocity-time graph for a skydiver approaching terminal velocity, what happens to the acceleration as terminal velocity is reached?

The acceleration (the gradient of the graph) decreases , becoming zero once terminal velocity is reached.

Define light gates in this experiment.

Light gates are positioned either side of the glass tube to start and stop the timer as the ball-bearing passes through, allowing the time, t , taken to fall the height, h , to be measured.

What are the independent and dependent variables in the determination of g experiment?

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

What variables are controlled in the determination of g experiment?

Same steel ball-bearing Same electromagnet Same distance between the ball-bearing and the top of the glass tube

In the determination of g experiment, the metre ruler used to measure height has a resolution of .......... , and the timer used to measure time has a resolution of .......... .

In the determination of g experiment, the metre ruler used to measure height has a resolution of 1 mm , and the timer used to measure time has a resolution of 0.01 s .

How is the ball-bearing released to begin falling in the determination of g experiment?

The current to the electromagnet is switched off, releasing the ball-bearing that was held beneath it.

When 2 h / t is plotted against t for the determination of g experiment, what do the gradient and the y-intercept represent?

y-axis = 2 h / t x-axis = t Gradient = acceleration due to gravity, g y-intercept = 2 u (twice the initial velocity)

True or False? In the determination of g experiment, the y-intercept of the graph of 2 h / t against t represents the acceleration due to gravity, g .

False. The gradient of the graph represents the acceleration due to gravity, g ; the y-intercept represents 2 u , twice the initial velocity.

A LevelPhysicsAQAFlashcardsMechanics & MaterialsEquations of Motion

Equations of Motion (AQA A Level Physics): Flashcards

Exam code: 7408

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FrontMotion Along a Straight Line
Define distance.
FrontMotion Along a Straight Line
Distinguish between speed and velocity.
BackMotion Along a Straight Line
Speed is a scalar quantity: the total distance travelled per unit of time
Velocity is a vector quantity: the rate of change of displacement of an object

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Cards in this collection (55)

Define distance.
Distance is the total length between two points. It is a scalar quantity (magnitude only).
Define displacement.
Displacement is the distance of an object from a fixed point in a specified direction. It is a vector quantity.
Distinguish between speed and velocity.
- Speed is a scalar quantity: the total distance travelled per unit of time
- Velocity is a vector quantity: the rate of change of displacement of an object
Acceleration is the rate of change of .......... of an object.
Acceleration is the rate of change of velocity of an object.
How do you find the instantaneous velocity of an object at a given point on a displacement-time graph?
Draw a tangent to the curve at the required time, then calculate the gradient of that tangent.
Define average speed.
Average speed is the total distance travelled divided by the total time taken.
True or False?
A distance-time graph can show negative values on the distance axis.
False.
Distance is a scalar quantity, so a distance-time graph can only have positive values. Only a displacement-time graph can show negative values, since displacement is a vector.
On a velocity-time graph, what does the gradient represent, and what does the area under the graph represent?
- Gradient: acceleration
- Area under the graph: displacement (or distance) travelled
On an acceleration-time graph, what does the area under the graph represent, and what does the gradient represent?
- Area under the graph: change in velocity
- Gradient: this is meaningless on an acceleration-time graph
What does the gradient of a displacement-time graph represent, and what does the gradient of a velocity-time graph represent?
- Displacement-time graph gradient = velocity
- Velocity-time graph gradient = acceleration
What does the area under a velocity-time graph represent, and what does the area under an acceleration-time graph represent?
- Velocity-time graph area = displacement
- Acceleration-time graph area = velocity
At the highest point of a bouncing ball's motion (point A), the ball momentarily has zero ...........
At the highest point of a bouncing ball's motion (point A), the ball momentarily has zero velocity.
At the lowest point of a bouncing ball's motion (point B), how does its velocity change?
The velocity changes instantaneously from negative to positive (the direction reverses), but the speed (magnitude) remains the same.
True or False?
At the lowest point of a bouncing ball's motion (point B), the ball has zero acceleration because it is momentarily at rest.
False.
The ball is only momentarily at rest at the highest point (point A). At the lowest point (point B), its velocity reverses direction almost instantaneously, which causes a momentary acceleration.
What assumption allows a bouncing ball to reach the same height on each bounce?
That there are no other forces, such as air resistance, acting on the ball.
Define the SUVAT equations.
The SUVAT equations are the equations of motion used for objects undergoing constant (uniform) acceleration.
What do the five SUVAT variables represent?
- s = displacement (m)
- u = initial velocity (m s^-1)
- v = final velocity (m s^-1)
- a = acceleration (m s^-2)
- t = time (s)
Which of the five SUVAT quantities is not a vector quantity?
Time, t, is not a vector. All the other quantities (s, u, v, a) are vector quantities and so can be positive or negative depending on direction.
If a question states that an object 'starts from rest', this means the initial velocity, u, is ...........
If a question states that an object 'starts from rest', this means the initial velocity, u, is zero.
What value is used for acceleration, a, if an object is described as 'falling due to gravity'?
a = g = 9.81 m s^-2
Under what condition are the SUVAT equations valid?
They are valid only for motion with constant (uniform) acceleration in a straight line.
True or False?
When using SUVAT equations, upwards must always be taken as the positive direction.
False.
It does not matter which direction is taken as positive, as long as the sign convention is applied consistently to all vector quantities throughout the problem.
Define a projectile.
A projectile is a particle moving freely (non-powered), under gravity, in a two-dimensional plane.
In projectile motion, what are the horizontal and vertical components of an initial velocity u at angle θ to the horizontal?
- Horizontal component = u cos θ
- Vertical component = u sin θ
In projectile motion, the horizontal and vertical components of displacement, velocity and acceleration are .......... of each other.
In projectile motion, the horizontal and vertical components of displacement, velocity and acceleration are independent of each other.
For a projectile launched and landing at the same height, what fraction of the total time of flight has elapsed when it reaches maximum height?
Half of the total time of flight.
What are the horizontal velocity and horizontal acceleration of a projectile (ignoring air resistance)?
- Horizontal velocity is constant
- Horizontal acceleration is zero
True or False?
At maximum height, a projectile's horizontal velocity is zero.
False.
At maximum height, the vertical velocity is zero (the projectile is momentarily at rest vertically). The horizontal velocity remains constant throughout the flight.
How does air resistance affect the range and maximum height of a projectile?
- Reduces the horizontal component of velocity, decreasing the range
- Reduces the maximum height reached
- Causes a steeper gradient as the projectile falls back to the ground
What two main factors affect the motion of an object moving through a fluid?
- Mass: a greater mass means a greater weight
- Surface area: a larger surface area means a greater air resistance
Define a drag force.
A drag force is a force that opposes the motion of an object moving through a fluid (gas or liquid), for example friction or air resistance.
What effect can a drag force never have on a moving object?
A drag force can never speed an object up or start it moving; it can only slow an object down or keep it moving at a constant speed.
What is lift, and which Newtonian principle explains it?
- Lift is an upwards force on an object moving through a fluid, perpendicular to the fluid flow
- It arises from Newton's third law: as, for example, an aeroplane pushes down on the air, the air exerts an equal and opposite upward reaction force on it
Drag forces convert kinetic energy into .......... and ...........
Drag forces convert kinetic energy into heat and sound.
True or False?
A drag force acting on an object stays the same size no matter how fast the object moves.
False.
Drag force increases as the speed of the object increases.
Define air resistance.
Air resistance is a drag force experienced by an object as it moves through air.
Besides speed, what factors affect the air resistance (and so the maximum speed) of a moving object?
- Cross-sectional area
- Shape
- Altitude
- Temperature
- Humidity
Why does a person swimming at walking pace use up far more energy than a person walking at the same pace?
Because air is around 800 times less dense than water, so air resistance has little effect at walking pace, whereas water resistance is much greater at the same speed.
How does air resistance affect a projectile's range and maximum height?
Air resistance decreases the horizontal component of velocity, which reduces both the range and the maximum height of the projectile compared to its motion without air resistance.
Define terminal velocity.
Terminal velocity is the maximum, constant velocity reached by a falling body when the drag force acting on it becomes equal to its weight.
As a falling body speeds up from rest, what happens to the drag force acting on it, and why does this cause its acceleration to decrease?
The drag force increases as the body's velocity increases. By Newton's second law ( $F = m a$ ), this reduces the resultant force on the body, so its acceleration decreases.
A falling body has reached terminal velocity when the drag force acting on it is .......... to its weight.
A falling body has reached terminal velocity when the drag force acting on it is equal to its weight.
Two skydivers, A and B, jump from a plane. Skydiver A is heavier than skydiver B. Which skydiver has the higher terminal velocity, and why?
Skydiver A has the higher terminal velocity. A greater mass means a greater weight, and terminal velocity is reached when weight equals drag force, so a greater weight requires a greater speed to balance it.
True or False?
When a skydiver deploys their parachute, they move upwards before continuing to fall.
False.
The skydiver does not move upwards; they decelerate from their higher terminal velocity to a new, lower terminal velocity.
On a velocity-time graph for a skydiver approaching terminal velocity, what happens to the acceleration as terminal velocity is reached?
The acceleration (the gradient of the graph) decreases, becoming zero once terminal velocity is reached.
Define light gates in this experiment.
Light gates are positioned either side of the glass tube to start and stop the timer as the ball-bearing passes through, allowing the time, t, taken to fall the height, h, to be measured.
What are the independent and dependent variables in the determination of g experiment?
- Independent variable = height, h
- Dependent variable = time, t
What variables are controlled in the determination of g experiment?
- Same steel ball-bearing
- Same electromagnet
- Same distance between the ball-bearing and the top of the glass tube
In the determination of g experiment, the metre ruler used to measure height has a resolution of .........., and the timer used to measure time has a resolution of ...........
In the determination of g experiment, the metre ruler used to measure height has a resolution of 1 mm, and the timer used to measure time has a resolution of 0.01 s.
How is the ball-bearing released to begin falling in the determination of g experiment?
The current to the electromagnet is switched off, releasing the ball-bearing that was held beneath it.
When 2h/t is plotted against t for the determination of g experiment, what do the gradient and the y-intercept represent?
- y-axis = 2h/t
- x-axis = t
- Gradient = acceleration due to gravity, g
- y-intercept = 2u (twice the initial velocity)
True or False?
In the determination of g experiment, the y-intercept of the graph of 2h/t against t represents the acceleration due to gravity, g.
False.
The gradient of the graph represents the acceleration due to gravity, g; the y-intercept represents 2u, twice the initial velocity.
What systematic error occurs in the determination of g experiment, and what is its effect?
Residual magnetism remains in the electromagnet after the current is switched off, causing the recorded time, t, to be longer than it should be.
State three random errors in the determination of g experiment.
- Large uncertainty in h from using a metre ruler with a precision of 1 mm
- Parallax error when reading h
- The ball-bearing may not fall accurately down the centre of each light gate
How is the fractional uncertainty in g determined from the graph in the determination of g experiment?
- A line of worst fit (the steepest line that still passes through all the error bars) is drawn
- The fractional uncertainty in g is the difference between the gradients of the lines of best fit and worst fit, divided by the gradient of the line of best fit

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