Question

7.
A ball is thrown vertically upward with speed 10 m/s and it returns to ground with speed 8 m/s.
There exists a constant air resistance. The maximum height attained by the ball will be
(
a) 4.1 m
b) 5.1 m
c) 6.1 m
d) 7.1 m​

Answer 1

Answer :-

5.1m

Explanation :-

Given :

Initial velocity of the ball,u => 10m/s

Final velocity of the ball,v => 0m/s

To Find :

Maximum height attained by the ball,s = ?

Solution :

According the third law of motion

$\sf{}v^2=u^2+2as$

Put their vlues and solve for “s”

$\sf{}\implies 0=10^2+2\times -9.8\times s$

$\sf{}\implies 0=100-19.6\times s$

$\sf{}\implies -100=-19.6\times s$

$\sf{} \implies \dfrac{-100}{-19.6}=s$

$\sf{} \therefore s=5.1m$

Therefore,(option b) 5.1m is the maximum height attain by the ball

☆Know more☆

$\sf{}First\ equation\ of\ motion:\ v=u+at$

$\sf{}Second\ equation\ of\ motion:\ s=ut+\dfrac{1}{2}at^2$