Motion/Kinematics

Question 1

Define speed

Answer 1

Speed is defined as the rate of change of distance.

Question 2

Define acceleration

Answer 2

Acceleration is defined as the rate of change of velocity.

Question 3

The braking distance of the car is proportional to…

Answer 3

the square of the initial speed of the car, u^2 .

Question 4

Why is the initial speed of the car proportional to the braking distance of the car?

Answer 4

In order for the car to stop, all of its kinetic energy must be dissipated by the brakes, and kinetic energy = ½ mv2.

Question 5

What factors affect the braking distance of a car

Answer 5

As well as the initial speed of the car, the braking distance is also increased by poor road conditions (e.g icy, wet), and the car conditions (e.g bald tyres, poor brakes, heavy load).

Question 6

What is displacement in terms of distance

Answer 6

the shortest direct distance between a starting point and ending point.

Question 7

the symbol for distance is

Answer 7

x

Question 8

what is the symbol for displacement

Answer 8

s

Question 9

acceleration is the rate of change of speed. True or False.

Answer 9

False

Question 10

What’s the thinking distance

Answer 10

The thinking distance is the distance that the vehicle travels while the driver is reacting to a stimulus before applying brakes.

Question 11

What’s reaction time

Answer 11

The reaction time is the time it takes for a person to react to a stimulus (e.g. the time it takes a driver to observe an obstacle and apply the brakes).

Question 12

What’s the equation used in an experiment used to measure the time taken for an object to fall from air between 2 light gates?

Answer 12

s=ut+1/2at^2

Question 13

After timing how long it takes the ball to fall through distance ‘q’ on the previous question, the results are plotted on a line graph. If the time ‘t’ is plotted on the x-axis, what quantity will correspond to the y-intercept?

Answer 13

s=q=ut+1/2at^2
We have rearranged the equation to be 2q/t = 2u + gt.
This is of the form y = gt + c where c = 2u, so the answer is (d).
The y-intercept would be ‘0’ if the distance was measured from when the ball was initially dropped (rather than when it dropped through the first hatch).
The time ‘t’ is the independent variable that is plotted on the x-axis.
The gravitational acceleration ‘g’ is the gradient of the graph.