Motion and Forces

Question 1

Describe how motion can be described.

Answer 1

Motion can be described in terms of position, speed or location.

Question 2

Define distance and displacement.

Answer 2

Distance: the length of a path.
Displacement: the linear distance between the initial/final position of an object.

Question 3

Describe reaction time/distance.

Answer 3

The time elapsed/distance travelled between a stimulus and a response.
Typically 1 second.

Question 4

Describe factors that affect reaction time.

Answer 4

• Factors that affect bodily operation:
• vehicle speed
• driver fatigue
• drugs and alcohol
• distraction

Question 5

Describe braking time/distance

Answer 5

The time elapsed/distance travelled after the brakes are applied for a vehicle to come to a full stop.

Question 6

Describe factors that affect braking time.

Answer 6

• Factors that affect vehicle operation:
• vehicle speed
• road conditions (icy, wet, gravel)
• worn tyres.

Question 7

Describe stopping distance.

Answer 7

The distance a vehicle travels between a stimulus and coming to a stop.

Stopping distance = reaction distance + braking distance.

Question 8

Define speed and provide the formula for providing speed.

Answer 8

Speed is how quickly an object is able to move from one place to another.

Speed = distance / time

Question 9

How to convert speed from km/h and m/s.

Answer 9

km/h / 3.6 = m/s

m/s x 3.6 = km/h

Question 10

List some methods of measuring speed.

Answer 10

• ticker timers
• radar guns
• ultrasonic sensors
• laser gun
• light gate

Question 11

Describe ticker timers.

Answer 11

• create representations of motion in a straight line.
• a strip of paper is passed through the machine, marking the paper at regular intervals.
• 50 dots per second, 0.2 seconds per dot
• speed = distance between 5 dots / 0.1 (d/t)

Question 12

List the advantages and disadvantages of ticker timers.

Answer 12

Advantages:
- cheap
- low technical knowledge required.

Disadvantages:
- mechanical errors (paper jam)
- doesn’t register stationary or backward motion..

Question 13

Describe the features of a speed time graph.

Answer 13

Demonstrates changes in speed over time.

Gradient = (final speed - initial speed) / time.

Acceleration = gradient.

Question 14

Describe the features of a distance time graph.

Answer 14

Demonstrates changes in distance of a moving object.

Gradient = distance / time.

Gradient = average speed.

Question 15

Define acceleration and provide the formula.

Answer 15

How quickly the velocity of an object changes.

Acceleration = (final velocity - initial velocity) / time.

Given in m/s/s.

Question 16

Define velocity.

Answer 16

The speed of an object in a given direction.

Question 17

Compare vector and scalar quantities.

Answer 17

Vector quantities measure magnitude and direction. E.g velocity, displacement.

Scalar quantities measure magnitude only. E.g speed, distance.

Question 18

Define force.

Answer 18

A push, pull, or twist on an object resulting when two objects interact. Measured in Newtons (N).

Question 19

Describe Net Force

Answer 19

Net force takes into account all forces acting upon an object and their directions.

Net Force = sum of all forces.

Question 20

Describe Vectors.

Answer 20

Arrows illustrating the size and direction of forces. Must be to scale.

Question 21

Describe balanced forces

Answer 21

Objects in balance (Net Force = 0) will not change motion. Will either:
- maintain a constant speed.
- remain stationary.

Question 22

Describe unbalanced forces.

Answer 22

Unbalanced object (Net Force ≠ 0) will change their state of motion:
- accelerate or decelerate.
- change direction.
- start/stop moving.

Question 23

Describe Newtons First Law.

Answer 23

An object in motion will stay in motion unless acted on by an unbalanced force.

Question 24

Provide examples of Newtons First Law.

Answer 24

• a car stops suddenly and items are ‘thrown forward’ as they continue in their state of motion.
• a car turns left and passengers lean right as they continue in a straight motion.
• an accelerating car requires the unbalanced force of the engine to begin moving.

Question 25

Describe Newtons Second Law.

Answer 25

The acceleration of an object is directly proportional to the net force and inversely proportional to its mass.

Net Force = Mass x Acceleration.

Question 26

Provide examples of Newtons Second Law.

Answer 26

• a tennis ball will accelerate faster than a netball when the same force is applied since it is lighter.
• a soccer ball will accelerate faster the more force that is applied.
• a truck requires more force than a car to accelerate.

Question 27

Describe Newtons Third Law.

Answer 27

For every action, there is an equal and opposite reaction.

Question 28

Provide examples of Newtons Third Law.

Answer 28

• when walking your foot pushes backwards and downwards against the ground and the ground exerts an equal and opposite force upwards and forwards against your food. This results in you moving forwards.
• a rocket engine pushes exhaust gases backwards and the rocked is pushed forwards.

Question 29

Describe the importance of friction in motion.

Answer 29

Friction provides a force in the opposite direction to overcome inertia and generate motion.

Question 30

Define inertia.

Answer 30

The tendency of an object to resist a change in its state of motion.