Question

A motorcycle of mass 100kg is moving on the straight line with the velocity 20m/s. Calculate it's kinetic energy.

Answer 1

Explanation:

Initial velocity of the car, u=90 km/h=25 ms

−1

;

Final velocity of the car, v=18 km/h=5 ms

−1

;

Time, t=4 s;

v=u+at

5=25+(a×4)

∴−a×4=20 or a=

4

−20

=−5ms

−2

Change in momentum, Δp=m(v−u)

=1200(5−25)=1200×(−20)=−24000Ns

Magnitude of force

Therefore, the force required, F=

t

m(v−u)

=

4

−24000

=−6000N

Answer 2

Answer:

A motorcycle of mass 100kg is moving on the straight line with a velocity of 20m/s, its kinetic energy is 20000J

Explanation:

The kinetic energy of an object with mass (m) moving with velocity (v) is given by the formula

$KE=\frac{1}{2}mv^{2}$

From the given question, we have

mass of the moving body $m=100kg$

the velocity of the body $v=20m/s$

put the values in the above equation

we get the kinetic energy of the body $KE=\frac{1}{2}*100*20^{2}=20000J$