Projectiles

Question 1

Modelling assumptions when dealing with projectiles

Answer 1

• the projectile is a particle
• gravity is constant
• flight is not powered
• effects of air resistance are negligible
• ignore any spin

Question 2

General equations for projectiles horizontally and vertically

Answer 2

horizontally:
x = (Vcosθ)t
ux = Vcvosθ
vx = Vcosθ
ax = 0
t = t
vertically:
y = (vsinθ)t - 1/2 gt^2
uy = Vsinθ
vy = Vsinθ - gt
ay = -g
t = t

Question 3

How to find the speed and direction of travel

Answer 3

For speed:
- focus on vx and vy
- speed = √vx^2 + vy^2
for direction:
α = tan^-1 (vy / vx)

Question 4

How to find the maximum height, time of flight and range

Answer 4

• the maximum height is when Vy = 0
• the time of flight is the value of t when y = 0
• the range on level ground is the value of x when y = 0

Question 5

Tips and advice for problem solving with projectiles

Answer 5

• draw a diagram
• choose the origin
• take care with signs
• use t to link info in one direction to a question in the other

Question 6

General equation of the trajectory of a projectile

Answer 6

x = (Vcosθ)t, y = (Vsinθ)t - 1/2 gt^2

Question 7

Advice when problem solving using the trajectory

Answer 7

translate the info from the question into a value for x or y and substitute into the equation