Question

calculate the work done by a force that changes the velocity of a moving body from 2 m/s to 5 m/s. Mass of the body is 20 KG​

Answer 1

Answer:

Kinetic energy is given by the expression,

(K. E)v = 1/2 mv2

Where,

K. E = Kinetic energy of the object

v = velocity of the object

Kinetic energy when the object was moving with a velocity of 5 m/s

(K. E)5 = 1/2 × 20 × (5)2

(K. E)5 = 250 J

Kinetic energy when the object was moving with a velocity 2 m/s

(K. E)2 = 1 /2 × 20 × (2)2

(K. E)2 = 40 J

Work done = Change in kinetic energy

= 40 J – 250 J

= – 210 J

Therefore, work done = -210 J

Answer 2

Answer:

Given : Initial velocity u=5 m/s

Final velocity v=2 m/s

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

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

$w = \frac{1}{2} \times 20 \times ( {2}^{2} - {5}^{2} )$

$w = - 210$