Bethany Ringel September 20
Summary #2: 2D Kinematics and Relative
Equations of Motion:
1. ∆d=¿ [(V f V)/2it
2. ∆d=¿ Vt + 0.5a t2
3. V f= V i a vector
4. V f V + 2i vector ∆d
5. ∆d=¿ Vtf– 0.5a vector
Always draw a diagram and write down your known variables.
Ex. A ball is thrown in the air from a height of 1.5m above the ground and takes
4s to drop. How fast was the ball thrown?
Acceleration due to gravity= -9.8m/s
t = 4s
Use one of the equations without V. f
1. ∆d=¿ Vti+ 0.5a vector
( ∆d−0.5a vector)/t = i
[(-1.5m-0.5(-9.8m/s)(4s) ]/4s = V i
V i 19.2m/s
Therefore the ball was thrown with an initial velocity of 19.2m/s upwards.
Always look at the x and y components when trying to solve projectile motion
questions. These components are independent of one another but are related by
time. Assuming air resistance is negligible and that the objects follow a path
determined solely by the acceleration due to gravity.
A motorcyclist drives off a 30m high cliff with a maximum spe