Projectile Motion

Question 1

state what it is meant by the key term - ‘projectile motion’

Answer 1

projectile motion is the motion observed when bodies are projected into the air and are under the influence of gravity (and air resistance) only

Question 2

what is the value of acceleration due to gravity on earth ?

Answer 2

• 9.81 m/s^2

Question 3

state what it is meant by the key term - ‘projectile’

Answer 3

a projectile is a body that is undergoing projectile motion

Question 4

what can a projectile be in S+E ?

Answer 4

in S+E, a projectile can be an object (eg - equipment), a body, or both (a system)

Question 5

state what it is meant by the key term - ‘gravity’

Answer 5

gravity is the attraction influence (force) that pulls objects towards the earth’s surface

Question 6

state what it is meant by the key term - ‘air resistance’

Answer 6

air resistance is a frictional force that occurs when air pushes over the surface of a body

Question 7

state an expansionary fact about ‘gravity’

Answer 7

gravity uniformly accelerates a projectile towards the earth’s surface at - 9.81 m/s^2

Question 8

state 2 expansionary facts about ‘air resistance’

Answer 8

1. limits the motion of a projectile

2. compared to gravity, air resistance is often minimal/negligible, so is often neglected

Question 9

state what it is meant by the key term - ‘trajectory’

Answer 9

trajectory - the flight path of an object through the air

Question 10

state what it is meant by the key term - ‘parabola’

Answer 10

parabola - the trajectory follows a ‘parabolic’ curve shape that is symmetrical about its apex

Question 11

state what it is meant by the key term - ‘apex’

Answer 11

apex - the highest point reached by a projectile

Question 12

state what it is meant by the key term - ‘range’

Answer 12

range - the horizontal displacement of a projectile

Question 13

state the 3 determinants of projectile motion

Answer 13

1. projection angle
2. projection velocity
3. projection height

Question 14

state the 2 influences imposed by the projection angle

Answer 14

1. the angle at release determines the shape of the trajectory, all other factors being equal
2. projectile angle influences the relative magnitude of the vertical and horizontal components

Question 15

a positive angle is > 0’, state 2 facts

Answer 15

1. between 0-90 degrees = oblique trajectory

2. parabolic shape, symmetrical about the apex

Question 16

0 degrees = horizontal trajectory (horizontal with the ground). state 2 facts

Answer 16

1. if no projection height, there will be no flight

2. if projection height, trajectory resembles one half of a parabola

Question 17

90 degrees, vertical trajectory. state 1 fact

Answer 17

projectile follows the flight path up and down with no range

Question 18

a negative angle is < 90 degrees, below horizontal. state 1 fact

Answer 18

not considered for projectile motion

Question 19

state what it is meant by the key term - ‘projectile velocity’

Answer 19

projectile velocity determines the height and range of a projectile, all other things being equal

Question 20

what determines the height and time of flight ?

Answer 20

vertical velocity (Vy) determines the height and time of flight

Question 21

what is the formula for Vy ?

Answer 21

Vy = V x sin(θ)

Question 22

what is the formula for ‘time of flight’ ?

Answer 22

Δt = 2 x ((Vy,f - Vy,i) / a)

Question 23

state the 2 formulae to work out maximum height

Answer 23

displacement (s) = (Vy,i x Δt) + 1/2 x a x Δt

displacement (s) = (Vy,f^2 - Vy,i^2) / (2 x a)

Question 24

what does horizontal velocity determine ?

Answer 24

horizontal velocity determines the range

Question 25

what is the formula for horizontal distance ?

Answer 25

Vx = V x cos(θ)

Question 26

state what it is meant by the key term - ‘projection height’

Answer 26

projection height is the relative distance between the point of release and the point of landing

Question 27

state 5 key features about projection height = 0

Answer 27

1. symmetrical about apex
2. parabolic
3. time up = time down
4. displacement up = displacement down
5. max range produced at 45 degree angle

Question 28

state 6 key features about projection height > 0

Answer 28

1. non-symmetrical about apex
2. parabolic
3. time up < time down
4. displacement up < displacement down
5. can be manipulated by technique to provide a mechanical advantage
6. optimal projection angle = < 45 degrees

Question 29

state 6 key features about projection height < 0

Answer 29

1. non-symmetrical about apex
2. parabolic
3. time up > time down
4. displacement up > displacement down
5. generally a disadvantage for projectile motion imposed by the nature of the task
6. max range produced with a projection angle > 45 degrees

Question 30

state the 3 goals for projectiles in sport

Answer 30

1. predicting a trajectory (eg - receiving a pass)
2. controlling a trajectory (eg - shooting)
3. maximising/optimising aspects of a trajectory (eg - throwing events)

Question 31

state 3 facts to explain the problems we encounter with the shot put when talking about projectile motion

Answer 31

1. theory suggests that a projection height > 0 has an optimal release height of < 45 degrees
2. for a typical elite throw, release height of 2.15 m, optimal angle should be 42 degrees
3. but, elite throwers release at 37 degrees

Question 32

what does it mean when it says release angle, height and velocity are not independent ?

Answer 32

changing one will effect the others

Question 33

what is the first SUVAT equation ?

Answer 33

v = u + at

Question 34

what is the second SUVAT equation ?

Answer 34

s = ut + 1/2 at²

Question 35

what is the third SUVAT equation ?

Answer 35

v² = u² + 2as

Question 36

what is the fourth SUVAT equation ?

Answer 36

s = (v + u / 2) x t

Question 37

what is the fifth SUVAT equation ?

Answer 37

s = vt - 1/2 at²