Projectile Motion

Question 1

What is projectile motion

Answer 1

Projectile motion is the movement of a body through the air following a curved flight path under the forces of gravity

Question 2

What is a projectile?

Answer 2

A body that is launched in the air, losing contact with the ground surface such as a discus or long jumper

Question 3

What factors affect the horizontal distance travelled by a projectile?

Answer 3

• Speed of release
• Angle of release
• Height of release

Question 4

How does speed of release affect horizontal distance travelled by a projectile?

Answer 4

Due to Newtons 2nd law of acceleration, the frater the force applied to a projectile, the greater change in momentum and therefore acceleration of the projectile into the air.
The greater the outgoing speed, the further it will travel

Question 5

How does angle of release affect horizontal distance travelled by a projectile

Answer 5

45 degrees is the optimum angle for a projectile with the same release and landing height to produce the greatest horizontal distance travelled.
If the release height is higher than the landing height (javelin, shot, discus), the optimum angle will be less than 45 degrees (dependent on the height) to produce the greatest horizontal distance.

Question 6

How does height of release affect horizontal distance travelled by a projectile

Answer 6

The higher the height of release, the further the horizontal distance travelled

Question 7

What is the optimum angle of release for a projectile

Answer 7

45 degrees if landing and release height are the same
Less than 45 degrees if the release height is higher than landing height

Question 8

Describe what a parabolic flight path is

Answer 8

A flight path that is symmetrical about its highest point, caused by the dominant weight force of a projectile

Question 9

Describe what a non parabolic flight path is

Answer 9

A flight path that is asymmetrical about its highest point, caused by the dominant force of air resistance

Question 10

What factors affect the shape of a flight path

Answer 10

Weight and air resistance

Question 11

Draw a free body diagram showing the start, middle and end of a flight for a shot putt

Answer 11

Question 12

Draw a free body diagram showing the start, middle and end of a flight for a badminton shuttle cock

Answer 12

Question 13

What is meant by ‘parallelogram of forces’

Answer 13

A parallelogram illustrating the theory that a diagonal drawn from the point where forces are represented in size and direction shows the resultant force acting

Question 14

What is meant by resultant force

Answer 14

The sum of all the forces acting on a body or the net force acting on the projectile

Question 15

Define Bernoulli’s principle

Answer 15

Creation of an additional lift force on a projectile in flight resulting from Bernoulli’s conclusion that the higher the velocity of air flow, the lower the surrounding pressure

Question 16

What is a lift force

Answer 16

An additional force created by a pressure gradient forming on opposing surfaces of an aerofoil moving through a fluid

Question 17

What is meant by ‘angle of attack’

Answer 17

The most favourable angle of release for a projectile to optimise lift force due to Bernoulli principle

Question 18

Draw a diagram to show how lift force us created on a discus in flight.
Include:
- Direction of motion arrow
- Direction of air flow arrow
- Pressure of air on top
- Pressure of air on bottom
- Velocity of air on the top
- Velocity of air on the bottom
- Direction of the lift force

Answer 18

Question 19

What is the Magnus effect

Answer 19

Creation of an additional Magnus force on a spinning projectile which deviates from the flight path

Question 20

Define Magnus force

Answer 20

A force created from a pressure gradient on opposing surfaces of a spinning body moving throughout the air

Question 21

What are different types of spin

Answer 21

Top spin
Back spin
Side spin - Hook
Side spin - Slice

Question 22

To which side of the centre of mass is force applied to create a hook

Answer 22

Eccentric force a applied to the right of the centre of mass
The ball spins left around the longitudinal axis

Question 23

To which side of the centre of mass is force applied to create a slice

Answer 23

Eccentric force a applied to the left of the centre of mass
The ball spins right around the longitudinal axis

Question 24

What happens to the flight path of a ball that has topspin?

Answer 24

The topspin creates a downwards Magnus force, shortening the flight path

Question 25

What happens to the flight path of a ball that has backspin

Answer 25

A backspin rotation creates an upwards Magnus force, lengthening the flight path

Question 26

What happens to the flight path of a ball that has hook spin?

Answer 26

Creates a Magnus force, swerving the projectile to the left

Question 27

What happens to the flight path of a ball that has slice spin

Answer 27

Creates a Magnus force, swerving the projectile to the right

Question 28

What happens to a ball hit with backspin after it hits the floor/ bounces

Answer 28

As a ball with backspin bounces, it decelerates, and bounces at a steeper angle

Question 29

Draw a diagram to show the effect of topspin on a ball
Include:
- Direction of motion arrow
- Direction of air flow arrow
- Pressure of air on top
- Pressure of air on bottom
- Velocity of air on the top
- Velocity of air on the bottom
- Direction of the Magnus effect

Answer 29

Question 30

Draw a diagram to show the effect of backspin on a ball
Include:
- Direction of motion arrow
- Direction of air flow arrow
- Pressure of air on top
- Pressure of air on bottom
- Velocity of air on the top
- Velocity of air on the bottom
- Direction of the Magnus effect

Answer 30