Question

A ball of mass 1.5kg is moving with a speed of 20m/s. Find its kinetic energy. If a force changes its speed to 25m

s-1, find the work done by this force.​

Answer 1

Answer:

KE = KE 1-KE 2

1/2mv2²-1/2mv1²

where m=1.5kg

v1=20m/s

v2=25m/s

so,

1/2×1.5×25×25-1/2×1.5×20×20

168.7J

Answer 2

Given

Initial Velocity = 20 m/s

Mass = 1.5 kg

Final Velocity = 25 m/s

To Find

Initial Kinetic Energy

Work done in changing the speed

Solution

● Kinetic Energy is given by, KE = ½mv² or ½mu²

✭ Initial Kinetic Energy

→ KE = ½mu²

→ KE = ½ × 1.5 × 20²

→ KE = ½ × 1.5 × 400

→ KE = 200 × 1.5

→ KE (Initial) = 300 J

✭ Final Kinetic Energy

→ KE = ½mv²

→ KE = ½ × 1.5 × 25²

→ KE = ½ × 1.5 × 625

→ KE (Final) = 468.75 J