Chapter 3 Motion

Question 1

How do you calculate average speed?

Answer 1

Average Speed = Distance travelled / time taken

Question 2

How is a distance time graph plotted and what does it show?

Answer 2

Distance is on y axis
Time is on x axis

The gradient shows speed

Question 3

How is constant speed and a stationary object shown on a distance time graph?

Answer 3

Constant Speed - A straight sloping line

Stationary Object - A horizontal straight line

Question 4

What is instantaneous speed?

Answer 4

The speed of car over a very short interval of time

Question 5

How is instantaneous speed found on a distance time graph?

Answer 5

By drawing a tangent and determining its gradient

Question 6

How is average velocity calculated?

Answer 6

Average velocity = Change in displacement / time taken

Question 7

How is a displacement time graph plotted and what does it show?

Answer 7

Displacement is on y axis
Time is on x axis
Velocity is shown by the gradient or by drawing a tangent to the gradient

Question 8

What is acceleration?

Answer 8

The rate of change of velocity

Question 9

How is acceleration calculated?

Answer 9

Change in velocity / Change in time

Question 10

How is a velocity time graph plotted and what does it show?

Answer 10

Velocity is y axis
Time is x axis
Gradient shows acceleration
Area under graph shows displacement

Question 11

What do these show on a velocity time graph?

a straight line of positive gradient

a straight line of zero gradient

a straight line of constant negative gradient

a curve with changing gradient

Answer 11

Straight positive line - Constant acceleration

Straight 0 gradient line - Constant velocity or 0 acceleration

Straight negative line - Constant deceleration

Curve - Acceleration is changing

Question 12

How do work out displacement from linear and non-linear velocity time graphs?

Answer 12

Linear - Split into shapes and find area

Non-Linear - Count boxes

Question 13

What are the suvat equations?

Answer 13

v = u+at
v² = u² + 2as
s = ut + ½at² 
s = vt - ½at²
s = ½(u+v)t

Question 14

What does SUVAT stand for?

Answer 14

S = Displacement
U = Initial Velocity
V  = Final Velocity
A = Acceleration
T = Time

Question 15

What is stopping distance?

Answer 15

The total distance travelled from when the driver sees the reason to stop to when the vehicle stops

Thinking Distance + Braking Distance

Question 16

What is thinking distance?

Answer 16

Distance travelled between the moment when you first see a reason to stop, to the moment when you use the brake

Question 17

What is braking distance?

Answer 17

Distance travelled from the time the brake is applied until the vehicle stops

Question 18

What is the equation for thinking distance?

Answer 18

Thinking distance = Speed x reaction time

Question 19

What is free fall and what is the acceleration of free fall denoted by?

Answer 19

When an object is accelerating under gravity with no other force acting on it

denoted by g

Question 20

What is the value of g?

Answer 20

9.81ms–2

Question 21

What is a light gate?

Answer 21

Two light beams, one above the other connected to a timer so that when an object interrupts the light, the timer starts and when it passes the second one the timer stops.

Question 22

What happens when one ball is dropped vertically and one ball is thrown horizontally from the same height at the same time?

Answer 22

Both fall at the same rate as the vertical and horizontal components are independent of each other?

Question 23

Assuming no air resistance, what happens to the vertical velocity, vertical displacement/time of flight and horizontal velocity of a ball thrown horizontally?

Answer 23

Vertical velocity - Changes due to acceleration of free fall

Vertical displacement and time of flight - Can be calculated using suvat

Horizontal Velocity - Remains constant

Question 24

How do you calculate the magnitude of the actual acceleration in projectile motion?

Answer 24

Use pythagoras with the vertical and horizontal components

Question 25

How do you work out the horizontal and vertical component of a projectile fired at angle θ with initial velocity v?

Answer 25

Horizontal Component = vcosθ

Vertical Component = vsinθ