2.1 - Distance, speed, and acceleration

Question 1

What can forces change?

Answer 1

The position, shape or motion of an object.

Question 2

State the equation linking distance, speed and time. Give appropriate units.

Answer 2

Distance (m) = Speed (m/s) x Time (s)

Question 3

if a car travels 24m in 2 seconds, what is its speed?

Answer 3

Speed = distance travelled ÷ time

24 m ÷ 2 s = 12 m/s.

Question 4

What is the difference between speed and velocity?

Answer 4

Velocity has a direction

Question 5

State the equation linking displacement, velocity and time. Give appropriate units.

Answer 5

Velocity (m/s) = displacement (m) / time (s)

Question 6

What does displacement mean?

Answer 6

is the distance moved in a straight line from the starting position to the end.

Question 7

What are scalar measurements?

Answer 7

Measurements that have magnitude (size) only. (Direction is not important)

Question 8

What are vector measurement’s?

Answer 8

Measurements that have size and direction

Question 9

State the equation for the average acceleration of an object. Give appropriate units.

Answer 9

Acceleration (m/s^2) = Change in velocity (m/s) / Time taken (s)

Question 10

Find the acceleration of a car, if it starts at 10 m/s and it reaches 30 m/s in 4 seconds

Answer 10

The change in velocity is v – u, which is 30 – 10 = 20 m/s.

The acceleration is the change in velocity ÷ time, which is 20 m/s ÷ 4 s = 5 m/s2.

Question 11

A cyclist brakes and slows from 11 m/s to 3 m/s in 2 seconds. Calculate the acceleration of the bike

Answer 11

The change in velocity v – u = 3 – 11 = -8 m/s.

The acceleration = change in velocity ÷ time = -8 m/s ÷ 2 s = -4 m/s2.

Question 12

How can speed be calculated from a distance-time graph?

Answer 12

Speed is equal to the gradient of the graph

Question 13

What must be done to calculate speed at a given time from a distance-time graph for an a accelerating object?

Answer 13

Drawing a tangent to the curve at the required time.

Calculating the gradient of the tangent

Question 14

In a distance-time graph what does a horizontal line mean?

Answer 14

The object is standing still

Question 15

How do you determine the gradient of a line?

Answer 15

1) choose any two points on the line
2) draw a right-angled triangle from one to the other, using the line as the hypotenuse
3) determine the height and width of the triangle
4) gradient = acceleration
5) acceleration = velocity change / time
6) height/ width

Question 16

How can the distance travelled by an object be calculated from a velocity-time graph?

Answer 16

It is equal to the area under the graph

Question 17

What is shown by a velocity-time graph with respect to:

Acceleration
Deceleration
Constant speed
Speed is zero

Answer 17

Acceleration is shown by a straight rising line.
Deceleration is shown by a straight falling line.
Constant speed is shown by a horizontal line.
A horizontal line along the -axis shows the speed is zero, meaning that the vehicle has stopped, or is stationary.

Question 18

What is gradient =

Answer 18

gradient = acceleration

Question 19

What is the stopping distance of a vehicle equal to?

Answer 19

The sum of thinking distance and braking distance

Question 20

For a given braking distance, if the vehicles speed is increased, what can be said about its stopping distance?

Answer 20

The stopping distance is increased with an increase in speed.

Question 21

How does the speed of the vehicle affect braking and thinking distance?

Answer 21

Both thinking and braking (and hence overall stopping) distances are increased when the speed is increased (as more distance is travelled in the same reaction time, or under the same braking force)

Question 22

What is the thinking distance?

Answer 22

The distance travelled by the car while the driver is reacting.

Question 23

What is the braking distance?

Answer 23

The distance travelled by the car once the driver has put their foot on the brakes.

Question 24

Give a typical range of values for human reaction time?

Answer 24

0.2 -0.9 seconds

Question 25

What are some things that can effect a driver’s reaction time (thinking distance)?

Answer 25

1) speed
2) distractions, eg mobile phones
3) alcohol
4) drugs
5) tiredness
6) visibility

Question 26

What are some factors that can affect braking distance?

Answer 26

1) speed
2) worn brakes
3) wet road
4) mass of the car
5) worn tyres
6) icy road

Question 27

What are three safety features car have?

Answer 27

air bags
crumple zone
inertia wheel safety belts