An object is dropped from a 32 m tall building. How fast will it be going when it strikes the ground?

Question

how would I solve this in kinematic equation 3?

Answer 1

I'm not sure which of these equations, A or B, you're referring to:

A) Δy = V₀t + 1/2 a t² this is the traditional "3rd" equation according to HOLT.

You would first need to determine the time to fall.

Setting V₀=0 (since the object is dropped) and a=g. This yields:

t = √2Δy/g

Substitute that time into the 2nd equation: V_f=V₀+gt to solve for the final speed (which is asked for, as opposed to velocity, which would be negative because velocity is a vector and speed is not).

B) V_f² = V₀² + 2aΔy This is a much more straightforward way to solve for V_f,

Setting V₀=0 and a=g and Δy=32 you can easily solve for V_f