3.1 Motion

Question 1

Define speed
the equation used to calculate speed
the SI units for speed

Answer 1

Speed is defined as the rate of change of distance
Speed = distance/time
m/s

Question 2

Define displacement

Answer 2

The displacement of an object is the distance it has travelled in a given direction (so it is a vector with both direction and magnitude)

Question 3

Define velocity
the equation used to calculate velocity
the SI units

Answer 3

The velocity of an object is defined as the rate of change of displacement or speed in a given direction (making velocity a vector)
Velocity = change in displacement/time
m/s

Question 4

Define acceleration
the equation used to calculate acceleration
the SI units

Answer 4

Acceleration is defined as the rate of change of velocity (making it a vector)
Acceleration = change in velocity/time
m/s^2

Question 5

What does a straight horizontal line represent on a displacement time graph

Answer 5

a stationary object

Question 6

What does a line with a constant non zero gradient represent on a distance time graph

Answer 6

an object moving with constant velocity

Question 7

What does a curved line represent on a displacement time graph

Answer 7

Acceleration (if gradient is increasing)

Deceleration (if gradient is decreasing_

Question 8

What does a straight line represent on a velocity time graph

Answer 8

an object moving with constant velocity

Question 9

What does a line with a constant non zero gradient represent on a velocity time graph

Answer 9

An object that is accelerating (positive gradient)

Decelerating (negative gradient)

Question 10

What does the area under a velocity time graph represent

Answer 10

displacement

Question 11

What does the area under acceleration time graph represent

Answer 11

velocity

Question 12

Describe how the terminal velocity of an object can be determined using light gates

Answer 12

• set up light gates vertically and measure the distance between them
• Connect them to a data logger and then release an object from rest above them, measuring the time it takes for the object to travel between the two gates
• using the time and the known distance you can calculate the velocity of the falling object

Question 13

Describe how light gatrs can also be used to investigate conservation of momentum

Answer 13

• place two carts on a linear air track (to reduce friction) with repelling magnets so that they do not stick together
• Attach card to the top of each cart so that they break the beams of the light gates when they pass
• keep one cart stationary and push the other towards it measuring the velocity before the collision
• Then measure the velocity of both carts after the collision and calculate the momentum before and after

Question 14

Define ‘g’

Answer 14

The acceleration of free fall, g, is the acceleration of an object in response to the gravitational attraction between the Earth and the object
g = 9.81 ms^-2

Question 15

Describe the experiment in which one can determine ‘g’ using an electromagnet

Answer 15

• An electromagnet holds a steel ball suspended a measured distance above a surface then start a timer when the electromagnet is deactivated and stop it when the surface is hit
• As the ball was initially resting u=0
• The distance and the time are known so we can use the suvat equation:
  s=ut+1/2at^2
• Calculate a which in this case is g

Question 16

A ball is projected off a castle at 6m/s. How does its horizontal velocity change from its launch until it hits the ground

Answer 16

the horizontal velocity remains the same as there is no acceleration in the horizontal direction

Question 17

In projectile motion what is the vertical acceleration?

Answer 17

The vertical acceleration is equal to gravitational field strength downwards