A ball is projected upward from the ground with a speed of 50 m/s. Which of the following is the velocity of the ball just as it returns to the
ground?
-50 m/s
-9.8 m/s
0 m/s
9.8 m/s

(a) Initial velocity of ball (u)=50m/s, acceleration of ball =−g,

final velocity at the highest point (v)=0

So applying the 3rd equation of motion we get:

v  

2

=u  

2

−2gh  

max

⇒0=50  

2

−2×10×h  

max

⇒h  

max

=  

20

2500

=125m

(b) Let the time required to reach max height be t. Then applying 1st equation of motion we get:

v=u−gt

⇒0=50−10t

⇒t=5s

(c) Let speed at half of max height be V then:

V  

2

=50  

2

−2g  

2

125

⇒V  

2

=2500−1250=1250

⇒V=  

1250

=35.35m/s.

Step-by-step explanation:

the answer is a.

step-by-step explanation:

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