Abaseball is thrown from the roof of 21.6 m tall building with an initial velocity of magnitude 12.0 m/s and directed at an angle of 48.2 above the horizontal. what is the speed of the ball just before it strikes the ground? use energy methods and ignore air resistance.

23.8m/S

Explanation:

Given data:  h1 = 21.6m  v1 = 10.3 m/s

Angle = 48.2o

g = 9.8 m/s2

Speed of ball just before it strikes the ground.  

Using conservation of energy:

E1 = E2

Where, E1 = Initial energy,           E2 = Final energy

So, K1 + U1 = K2 + U2

Where, K1 = initial kinetic energy,   U1 = Initial potential energy

K2 = Final kinetic energy,      U2 = Final potential energy

recall K =1/2MV

car stops. he keeps going = he has inertia