Snowballs are thrown with a speed of 11 m/s from a roof 6.0 m above the ground. Snowball A is thrown straight downward; snowball B is thrown in a direction 20^\circ above the horizontal.

Question

1-Find the direction of motion of the two snowballs just before they land.

Answer 1

for ball A- it continues straight down

for ball B:
v= 11 sin 20 - g t
h = 6 + 11 sin 20 t - 4.9 t^2
when h = 0
0 = 6 + 3.76 t - 4.9 t^2
t^2 - .768 t - 1.22 = 0
t = [ .768 +/- sqrt (.59+4.88) ]/2
t = [ .768 +/- 2.33 ]/2
t = 1.55 seconds
v = 3.76 - 9.8 (1.55)
v = -11.43 vertical speed
u = 11 cos 20 = 10.33
so speed at h = 0 = sqrt(11.43^2+10.33^2)
and angle down from horizontal = tan^-1 (11.43/10.33)