Question

a constant force acting on a 20 kg mass change its velocity from 30 km per hour to 60 km per hour calculate work done by force​

Answer 1

Answer:

27000 J

Explanation:

Given :          Initial velocity     u=30km/h

                     Final velocity     v=60km/h

The work done is equal to the change in the kinetic energy of an object.

W= 1/2 m(v²-u²)

  = 1/2 × 20×(60²-30²)

  = 10×(3600-900)

  = 10×(2700)

  = 27000 J

Answer 2

Answer:

The work done by the force is 2085 J.

Explanation:

Work is the energy that is transferred to or from an object when force is applied along a displacement. Since work is a scalar quantity, it only has magnitude and no direction.

Given that:

Mass m = 20 kg

Initial velocity u = 30 km/hr = 30 × $\frac{5}{18}$ m/s = 8.33 m/s

Final velocity v = 60 km/hr = 60 × $\frac{5}{18}$ m/s = 16.67 m/s

We know that work done W = change in kinetic energy

∴W = $\frac{1}{2} mv^{2} - \frac{1}{2} mu^{2}$

      = $\frac{1}{2} m(v^{2} -u^{2} )$

      = $\frac{1}{2}$ × $20$ × ($16.67^{2} -8.33^{2}$)

      = $\frac{1}{2}$ × $4170$ = $2085$ J

Therefore the work done by the force is 2085 J.