Projectile Motion

Question 1

examples of projectile motion

Answer 1

• long jump
• high jump
• shot put
• ball toss
• running (flight phase)
• free throw

Question 2

force that acts before the object is a projectile

Answer 2

results in initial velocity

Question 3

after release, what external force acts on projectile?

Answer 3

only gravity (constant accel. = -9.81 m/s^2)

Question 4

uniform motion

Answer 4

velocity is constant, so acceleration = 0

Question 5

uniformly accelerated motion

Answer 5

object is undergoing constant acceleration (due to gravity)

Question 6

constant velocity

Answer 6

constant acceleration, accel-time curve is constant (slope = 0) and equal to -9.81 m/s^2

Question 7

T/F: horizontal and vertical components of velocity are independent and should be treated separately

Answer 7

True

Question 8

when is velocity at its peak in vertical motion of a projectile?

Answer 8

closer to the ground, right before it hits ground

Question 9

what is the initial and final velocity of a person who jumps up/out and lands on the ground?

Answer 9

initial v = positive
up: magnitude of v decreases
v at peak = 0
down: magnitude of v increases
final velocity = negative

Question 10

what shape is the path of a projectile?

Answer 10

parabola (when air resistance ignored)

Question 11

does the COM of a body or object follow the parabolic path even if there are complex motions of other segments?

Answer 11

yes

Question 12

time in air - for the same vertical take-off and landing positions

Answer 12

t up = t down

Question 13

horizontal displacement - for the same vertical take-off and landing positions

Answer 13

d H-up = d H-down

Question 14

displacement up vs. down - for the same vertical take-off and landing positions

Answer 14

d y-up = d y-down

Question 15

vertical velocity (up)

Answer 15

positive

Question 16

vertical velocity at peak height

Answer 16

v = 0

Question 17

vertical velocity (down)

Answer 17

negative

Question 18

is horizontal velocity of a projectile constant?

Answer 18

yes, it does not change during flight phase b/c there is no acceleration

Question 19

if a soccer ball has a horizontal velocity of 20 m/s what is the acceleration?

Answer 19

horizontal accel = 0

Question 20

what is the horizontal velocity of the soccer ball at t = 1,2,3,4,5 s?

Answer 20

no accel so v = 20 m/s at every instant

Question 21

what is the horizontal distance at t = 1,2,3,4,5 s?

Answer 21

v = 20 m/s so 20 m, 40 m, 60 m, 80 m, 100 m

Question 22

three factors that influence the trajectory of a projectile

Answer 22

1. projection angle
2. projection velocity
3. relative height of projection (h)

Question 23

what projection angle produces the largest horizontal displacement?

Answer 23

45 degree angle

Question 24

projection angle - maximal height

Answer 24

90 degrees

Question 25

projection angle - maximal distance

Answer 25

45 degrees

Question 26

what is the most important factor that influences horizontal displacement?

Answer 26

projection velocity

Question 27

if you increase velocity, what happens to displacement?

Answer 27

displacement increases

Question 28

projection height =

Answer 28

release height - landing height

Question 29

release ht = landing ht

Answer 29

projection height = 0

Question 29

release ht > landing ht

Answer 29

positive value

Question 30

release ht < landing height

Answer 30

negative value

Question 31

two factors that determine flight time

Answer 31

1. vertical speed at release
2. height of release

Question 32

take off position = landing position

Answer 32

t up = t down

Question 33

take off position > landing position

Answer 33

t up < t down

Question 34

take off position < landing position

Answer 34

t up > t down

Question 35

what happens when release height is greater?

Answer 35

• distance down increases
• time down increases
• horizontal distance increases (due to more time in air)

Question 36

what happens when landing height is greater?

Answer 36

• distance down decreases
• time down decreases
• horizontal distance decreases (due to less time in air)

Question 37

factors influencing flight time

Answer 37

1. initial vertical velocity
2. relative projection height

Question 38

factors influencing horizontal displacment

Answer 38

1. initial vertical velocity
2. relative projection height

Question 39

factors influencing trajectory

Answer 39

1. initial resultant velocity
2. projection angle
3. relative projection height