Physics 20: Planar kinematics

Question

A projectile is fired at 30.0 m/s off of a 50.0m cliff at 40.0 degrees above the horizon.

a. Determine the time (in s) in the air before it hits the ground.

b. Determine the distance (in m) from the bottom of the cliff it lands.

Answer 1

Time of flight

T = 2vSintheta /g = t1

=2*30*Sin40/g =find this time

Then initial vertical downward velocity from the top of cliff = V Sintheta = 30*Sin40=u

with this initial velocity it falls down

t2 = ? Use

s = u*t + 1/2 (gt^2)

plug in u = 30*Sin40

s= h =50 m

solve for t

this t=t2

add t1 and t2 to get total time in air