[ام عبد الرحمن محمد]

السؤال 13
The time to travel 36 m is given by
t = 36 / 20 cos 53 = 2.991 s.

In this time it travels a vertical height given by
h = 20 sin 53*2.991 – ½ * 9.8 *2.991^2
h =3.94 m

Since 3.94 m is more than 3.05 m
the ball is above the cross bar by a height of 0.89.

The velocity at the end of 2.991 s is
v = u –gt = 20 sin 53 – 9.8*2.991 = -13.34.
The negative sign shows that the ball is falling down
while approaching the cross bar.