Lecture 5 - Projectile Motion Flashcards
Projectile:
a body in free fall that is subject only to the forces of gravity and air resistance
We analyze the horizontal and vertical components of projectile motion separately because…
➢ 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
The force of gravity produces a constant acceleration of ___________ on bodies near the surface of the earth
-9.81m/s^2
True or False: The pattern of change in the vertical velocity of a projectile is symmetrical about the apex
True
Does the the magnitude of vertical velocity decrease or increase as the ball rises
decreases
Does the the magnitude of vertical velocity decrease or increase as the ball falls due to the influence of gravitational force
increases
Trajectory:
the flight path of the centre of gravity of a projectile
Factors that influence trajectory:
Angle of projection
Projection speed
Relative height of projection
At a 90 degree angle, will the projection increase or decrease until it reaches a projection angle at 45 degrees
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
What does the angle or projection refer to
direction of velocity at takeoff with respect to the
horizontal
What does projection speed refer to
speed at takeoff; magnitude of velocity
True or False: The faster the object is at takeoff, the longer and higher it will go
True
What does Relative height of projection refer to
comparison of the height of the object at
takeoff and after it lands
what is the optimum angle when the object is taking off and landing at the same height
The optimum angle is 45 degrees when the object is taking off and landing at the same height
what is the optimum angle when the object takes off higher than it lands
The optimum angle would be less than 45 degrees if the object takes off higher than it lands
what is the optimum angle when the object takes off lower than it lands
The optimum angle would be more than 45 degrees if the object takes off lower than it lands
Flight time is influenced by:
Initial vertical velocity
Relative projection height
Horizontal displacement (how far it travels/the range) is influenced by:
Horizontal velocity
Initial vertical velocity
Relative projection height
Peak height is influenced by:
Initial vertical velocity
Equations of Constant Acceleration
- V2 = V1 + at
- d = v1t + 1⁄2(at)^2
- V2^2 = v1^2 + 2ad
No horizontal forces, therefore ah (horizontal acceleration) = 0
This means =
This means no change in velocity, no acceleration
Until the object lands, the horizontal velocity remains the same
Vh2 = Vh1 (constant)
dh = Vh1t
Vh2 = Vh1 (constant)
Therefore:
dh = Vh1t
Vh = horizontal velocity
At the apex; the vertical velocity equals 0
g = acceleration due to gravity
Vy2 = Vy1 - 9.81t
Time to peak height is influenced only by Vy (vertical velocity) and and ‘g’
➢ Ta = Vy1/-9.81
The peak vertical displacement is related to Vy1^2
➢ dv = Vy1^2/2g
Practice Question 1 (Heidi’s notes)
