Question

A body is falling from height h it takes 8 sec to reach ground. The time it takes to cover the first one fourth of height is??

Answer 1

Answer:

4 second

Explanation:

The body is falling from height h, so its initial velocity should be 0 m/s.

It is free fall condition, so the acceleration due to gravity = 10 $\frac{m}{s^{2} }$.

Time taken to reach ground = 8 second

Since equation is               $s = ut + \frac{1}{2}at^{2}$

putting the values:           $s = 0*8 + \frac{1}{2} * 10 * 8^{2}$ = 320 meter

                             

$\frac{1}{4}$ of total 320 m height is =   $\frac{320}{4} = 80$

Now we have to calculate time to travel first 80 m.

Again,

The body is falling from height h, so its initial velocity should be 0 m/s.

It is free fall condition, so the acceleration due to gravity = 10 $\frac{m}{s^{2} }$.

distance travelled = 80 m

Since equation is               $s = ut + \frac{1}{2}at^{2}$

putting the values:           $80 = 0*t + \frac{1}{2} * 10 * t^{2}$

                                            $80 = 5t^{2}$        

                                             $16 = t^{2}$      

                              so,           $t = \sqrt{16} = 4 second$          

Answer 2

The time it takes to cover the first one fourth of height is t=4sec