Question

A projectile is fired from ground level with a speed of 40 m/s at an angle of 30 degrees and hits a building 100m away.
What is the time of flight of the projectile?
How high above ground does the projectile hit the building?
What is the speed of the projectile just before it strikes the building?

Answer 1

Vo = 40 m/s @ 30 Deg.
Xo = 40*cos30 = 34.6 m/s.
Yo = 40*sin30 = 20 m/s.

a. Tr = (Yf-Yo)/g,
Tr = (0-20) / -9.8 = 2.04 s. = Time to
rise to max ht.
Tf = Tr = 2.04 s. = Fall time.
Tr + Tf = 2.04 + 2.04 = 4.08 s. = Time of flight.

b. hmax = Yo*t + 0.5g*t^2,
hmax = 20*2.04 - 4.9(2.04)^2=20.4 m.

Yf = Yo + gt,
Yf = 0 + 9.8*2.04 = 20 m/s.= Final velocity before striking gnd.