3.1 Motion

Question 1

Instantaneous Speed

Answer 1

The speed at a certain time

Question 2

Displacement

Answer 2

A vector quantity that represents how far an object has travelled from its starting point in a given direction

Question 3

Average Speed

Answer 3

Distance / Time

Question 4

Average Velocity

Answer 4

Displacement / Time

Question 5

Distance

Answer 5

A scalar quantity that shows how far something travelled along a certain route

Question 6

Velocity

Answer 6

A vector quantity that shows rate of change of displacement

Question 7

Acceleration

Answer 7

A vector quantity, the rate of change of velocity

Question 8

Gradient of displacement-time graph

Answer 8

Velocity

Question 9

Gradient of velocity-time graph

Answer 9

Acceleration

Question 10

Area under velocity-time graph

Answer 10

Displacement

Question 11

The 4 SUVAT equations

Answer 11

v = u + at
s = 0.5(u + v)t
s = ut + 0.5at^2
v^2 = u^2 + 2as
(s = vt - 0.5at^2)

Question 12

value of g

Answer 12

9.81

Question 13

Acceleration of a body in free fall

Answer 13

-g

Question 14

Is horizontal velocity independent of vertical

Answer 14

yes

Question 15

The two types of approaches for measuring g

Answer 15

Direct e.g. timing a falling ball

Indirect e.g. timing a pendulum

Question 16

Describe the experiment to measure g (trapdoor)

Answer 16

• Set up a steel ball supported by an electromagnet
• Turn of current so ball is released and clock started
• When ball hits trap door a connection is broken and timer is stopped
• We now have u, s, t and want to find a so we can rearrange a SUVAT
• Can plot a graph with different values of s (and t)

Question 17

Potential sources of error for g trapdoor experiment (3)

Answer 17

• Electromagnet current too high can cause delay
• If distance is too large air resistance might have a noticeable effect
• Measurement of distance

Question 18

Experiment to measure g (light gates)

Answer 18

• A piece of card is dropped from a certain height above a light gate
• Light gate and data logger calculate v, u = 0, s = measured so a can be calculated
• A graph of v^2 against s can be plotted with the gradient being 2g

Question 19

Assumptions made by light gate g experiment

Answer 19

The cards velocity is constant as it travels through the gate

Question 20

Thinking distance

Answer 20

Distance a car travels between driver seeing hazard and applying brakes

Question 21

Braking Distance

Answer 21

Distance between applying brakes and coming to rest

Question 22

Stopping distance

Answer 22

thinking distance + braking distance

Question 23

Factors that increase thinking distance (5)

Answer 23

• high speed
• tiredness
• alcohol / drugs
• Distractions
• Age

Question 24

Factors that increase braking distance (5)

Answer 24

• high speed
• poor road conditions
• poor brake conditions
• poor tyre conditions
• mass of car

Question 25

Equation for thinking distance

Answer 25

reaction time * speed

Question 26

Relationship between braking distance and speed

Answer 26

squared

Question 27

Why is braking distance proportional to speed squared

Answer 27

Because brakes constantly do work against the car, and the total energy is 0.5mv^2

Question 28

Equipment used to investigate motion and collisions of objects

Answer 28

• Trolleys, light gates, data loggers

- Video recording and analysing frame by frame