Projectile motion, lift and Bernoulli principle

Question 1

Define ‘projectile motion’

Answer 1

The movement of body through the air following a curved flight path under the force of gravity

Question 2

What is a projectile?

Answer 2

A body launched into the air and so subjected to weight and air resistance

Question 3

What does a flight path show?

Answer 3

The start to finish and overall distance travelled after gravity has accelerated the body back to the ground

Question 4

What factors affect the horizontal distance travelled by a projectile?

Answer 4

Speed, height and angle of release and aerodynamic factors

Question 5

How does Newton’s second law to projectile motion using the example of a javelin

Answer 5

The greater the force applied to the javelin, the further the javelin will travel because the size of the force applied is proportional to the rate of change of momentum generated by the strength and speed of the performer

Question 6

If speed remains the same, how does the angle of release affect horizontal distance?

Answer 6

90 - vertically up and down with minimal travel
70 - peak height but rapid return to the ground, short distance of travel
45 - optimal angle of release to maximise horizontal distance
30 - projectile has insufficient height to maximise travel time, low to the ground

Question 7

If height of release is (1) the landing height, the angle of release is less than (2) because the projectile already has increased (3) e.g. javelin

Answer 7

1 - above
2 - 45 degrees
3 - flight time

Question 8

If the angle of release is below the (1), the optimal angle of release is (2) because the projectile needs an increased (3) e.g. (4) in golf

Answer 8

1 - landing height
2 - more than 45 degrees
3 - flight time
4 - bunker shot

Question 9

What are the different causes of parabolic and non-parabolic flight paths?

Answer 9

Parabolic: symmetrical as mass is dominant force
Non: unsymmetrical as air resistance is dominant

Question 10

Describe the flight path of a parabolic motion

Answer 10

High mass and low velocity
Weight is dominant
Symmetrical about highest point
Smooth surface area and small front c.s.a.

Question 11

Describe the flight path of a non-parabolic motion

Answer 11

Low mass and high velocity
Air resistance is dominant
Not symmetrical about highest point
Uneven surface area

Question 12

What are the five key pointers of drawing a free body diagram?

Answer 12

Direction of motion 
Acting forces
Where the forces originate 
Direction forces are acting 
Relative size of forces

Question 13

What are the two diagrams that could be asked to draw?

Answer 13

Parallelogram of forces

Free body diagram

Question 14

What is Bernoulli’s principle?

Answer 14

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

Question 15

Describe an aerofoil shape

Answer 15

Flat bottom and rounded top

Question 16

Describe the airflow around an aerofoil shape in flight

Answer 16

Above the aerofoil, air moves at a high velocity and low pressure, below the air move at a lower velocity and high pressure, the pressure gradient causes a lift force

Question 17

Describe the downward lift force

Answer 17

An aerofoil shape with a flatter upper surface and curved lower surface e.g. track cycling, they are streamlined to reduce air resistance and to generate additional force

Question 18

How is downward lift created in track cycling?

Answer 18

The airflow underneath the cyclist has to travel a greater distance and so travels at a greater velocity creating an area of low pressure, the pressure gradient generates a downward lift force increasing the effects of weight on the track maximising friction