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

Answer:

The speed of boy is 4.5 m/s

Explanation:

Given that,

Kinetic energy = 810 J

Mass = 80 kg

We need to calculate the speed

Using formula of kinetic energy

$K.E=\dfrac{1}{2}mv^2$

Where, m = mass

v = speed

Put the value into the formula

$810=\dfrac{1}{2}\times80\times v^2$

$v^2=\dfrac{2\times810}{80}$

$v=\sqrt{\dfrac{2\times810}{80}}$

$v=4.5\ m/s$

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