Question

a tennis ball is served horizontally 2.4m above the ground at 30m/s the net is 12m away and 0.9 m high calculate the time required by ball to reach the net? ​

Answer 1

Answer:

Data:

V0x= 30m/s

H1= 2.4 m

V0y= 0

X= 12m

H2= 0.9m

To find:

(a) Will the ball clear the net?

(B) X’= ?

Solution:

(a) X= V0x t

12=30 t

12/30 = t

t= 0.4 s

As, H=V0y t + ½ g t2

H= (0)(0.4)+1/2(-9.8)(0.4)2

H= -0.78m

-ve sign shows that the height of the ball at the net from the top.

Height of the ball at the net and from the ground= H1-H=2.4-0.78=1.62m

As 1.62m>0.9m so the ball will clear the net.

(B) H1= V0y t’ + ½ g t’2

-2.4= (0)t’ + ½ (-9.8) t’2

.

.

.

t’= 0.69s

X’=V0x t’

X’=(30)(0.96)

X’= 20.7m

This is the solution my teacher came up with and honestly I have no idea whats going on? :/