Question

if a body of 4kg is moving with velocity 5 m/s and after sometime its velocity become 8 m/s, then find the change in kinetic energyof the. body.
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Answer 1

Given :

• Mass of the body = 4 kg
• Initial velocity  of the body = 5 m/s
• Final velocity of the body = 8 m/s

To find :

• Change in kinetic energy

Solution :

Kinetic energy is the energy possesed by the body during it's motion .

Kinetic energy is given by the formula ,

KE = ½ mv²

here ,

• KE = kinetic energy
• m = mass
• v = velocity

Initially ,

⇒ KE = ½ mu²

⇒ KE = ½ x 4 x 5

⇒ KE = 2 x 5

⇒ KE = 10 J

Similarly ,

⇒ KE' = ½ mv²

⇒ KE' = ½ x 4 x 8

⇒ KE' = 2 x 8

⇒ KE' = 16 J

Change in kinetic energy

⇒ ΔKE = KE' - KE

⇒ ΔKE = 16 - 10

⇒ ΔKE = 6 J

Hence ,

The change in kinetic energy of the body is 6J .