Explained: "A ball is thrown upwards with an initial..."

High School
Physics
Force, Motion and Energy
Acceleration Due to Gravity

Aydin Welch

Answered question

2022-12-15

A ball is thrown upwards with an initial velocity of

20 m s^{- 1}

. Find the time of flight and the maximum height reached by the body respectively. (

g = 10 m s^{- 2}

)
A. 4s 20m
B.5s 25 m
C.4s 24m
D.5s 30 m

Answer & Explanation

Jonah Wood

Beginner2022-12-16Added 4 answers

Given:
initial speed,

u = 20 m s^{- 1}

Acceleration due to gravity,

g = - 10 m s^{- 2}

Positive movement is regarded as being upward.
At maximum height, velocity will be zero, (v = 0) as the ball will change the direction of motion. Let the maximum height be H.
Using third equation of motion,

v^{2} = u^{2} + 2 a s

0^{2} = 20^{2} + 2 \times (- 10) \times H

H=20 m
When the ball returns to the initial point, net displacement is zero. Let the time of flight be T. Using second equation of motion, we get:

s = u t + \frac{1}{2} a t^{2}

0 = 20 \times T + \frac{1}{2} \times (- 10) \times T^{2}

T=0 or T=4 s
Time of flight is more than zero. So, it is 4 s.

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