Question

•A ball is thrown up with a velocity of 20ms^-1. What is the time of flight, neglecting air resistance?
a. 8sec
b.1sec
c.2sec
d.4sec
​

Answer 1

Answer:

4 sec , D option

Explanation:

hope you get it but i send you explanation

Solution:-

When the body comes back to the initial position, the displacement s = 0

We know that,

s = ut – 1/2gt^{2}

2

\Longrightarrow⟹ s = ut – 1/2gt^{2}

2

\Longrightarrow⟹ 0 = ut – 1/2gt^{2}

2

\Longrightarrow⟹ ut = 1/2gt^{2}

2

t = 2u/g. Here ‘t’ is the time of flight, i.e., {t_a} + {t_d}t

a

+t

d

Therefore, Time of flight, t =

\frac{2 \times 20}{10} = 4s

10

2×20

=4s

Thus, time of flight neglecting the air resistance = 4s