Question

A boy is running with a kinetic energy of 810 j if the boy has a mass of 80 kg whats his speed?

Answer 1

If the boy started at rest then its speed would be equal to 4.5 m/s squared. 

Answer 2

The speed of boy is 4.5 m/s

Step-by-step explanation:

Given that,

Kinetic energy = 810 J

Mass = 80 kg

We need to calculate the speed

Using formula of kinetic energy

`K.E=(1)/(2)mv^2`

Where, m = mass

v = speed

Put the value into the formula

`810=(1)/(2)*80* v^2`

`v^2=(2*810)/(80)`

`v=\sqrt{(2*810)/(80)}`

`v=4.5\ m/s`

Hence, The speed of boy is 4.5 m/s.