Lecture 5 - Projectile Motion

Question 1

Projectile:

Answer 1

a body in free fall that is subject only to the forces of gravity and air resistance

Question 2

We analyze the horizontal and vertical components of projectile motion separately because…

Answer 2

➢ Vertical is influenced by gravity and air resistance

➢ Horizontal is only influenced by air resistance, not gravity

➢ Air resistance is small and is often neglected

➢ Vertical and horizontal have different accelerations

Question 3

The force of gravity produces a constant acceleration of ___________ on bodies near the surface of the earth

Answer 3

-9.81m/s^2

Question 4

True or False: The pattern of change in the vertical velocity of a projectile is symmetrical about the apex

Answer 4

True

Question 5

Does the the magnitude of vertical velocity decrease or increase as the ball rises

Answer 5

decreases

Question 6

Does the the magnitude of vertical velocity decrease or increase as the ball falls due to the influence of gravitational force

Answer 6

increases

Question 7

Trajectory:

Answer 7

the flight path of the centre of gravity of a projectile

Question 8

Factors that influence trajectory:

Answer 8

Angle of projection
Projection speed
Relative height of projection

Question 9

At a 90 degree angle, will the projection increase or decrease until it reaches a projection angle at 45 degrees

Answer 9

At a 90 degree angle, the projection will increase until it reaches a projection angle at 45 degrees (this would be the longest trajectory)

the trajectory will decrease as the projection angle decreases

Question 10

What does the angle or projection refer to

Answer 10

direction of velocity at takeoff with respect to the
horizontal

Question 11

What does projection speed refer to

Answer 11

speed at takeoff; magnitude of velocity

Question 12

True or False: The faster the object is at takeoff, the longer and higher it will go

Answer 12

True

Question 13

What does Relative height of projection refer to

Answer 13

comparison of the height of the object at
takeoff and after it lands

Question 14

what is the optimum angle when the object is taking off and landing at the same height

Answer 14

The optimum angle is 45 degrees when the object is taking off and landing at the same height

Question 15

what is the optimum angle when the object takes off higher than it lands

Answer 15

The optimum angle would be less than 45 degrees if the object takes off higher than it lands

Question 16

what is the optimum angle when the object takes off lower than it lands

Answer 16

The optimum angle would be more than 45 degrees if the object takes off lower than it lands

Question 17

Flight time is influenced by:

Answer 17

Initial vertical velocity
Relative projection height

Question 18

Horizontal displacement (how far it travels/the range) is influenced by:

Answer 18

Horizontal velocity
Initial vertical velocity
Relative projection height

Question 19

Peak height is influenced by:

Answer 19

Initial vertical velocity

Question 20

Equations of Constant Acceleration

Answer 20

1. V2 = V1 + at
2. d = v1t + 1⁄2(at)^2
3. V2^2 = v1^2 + 2ad

Question 21

No horizontal forces, therefore ah (horizontal acceleration) = 0

This means =

Answer 21

This means no change in velocity, no acceleration

Until the object lands, the horizontal velocity remains the same

Vh2 = Vh1 (constant)

dh = Vh1t

Question 22

Vh2 = Vh1 (constant)

Therefore:

dh = Vh1t

Answer 22

Vh = horizontal velocity

At the apex; the vertical velocity equals 0

g = acceleration due to gravity

Question 23

Vy2 = Vy1 - 9.81t

Question 24

Time to peak height is influenced only by Vy (vertical velocity) and and ‘g’

➢ Ta = Vy1/-9.81

Question 25

The peak vertical displacement is related to Vy1^2

➢ dv = Vy1^2/2g

Question 26

Practice Question 1 (Heidi’s notes)