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.
Answers
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
✭ Work Done
→ Work = Final KE - Initial KE
→ Work = 468.75 - 300
→ Work = 168.75 J
Answer:
Given :-
- Mass of ball (M) = 1.5 kg =
- Initial velocity (U) = 20 m/s
- Final velocity (V) = 25 m/s
To find:-
❶ Initial kinetic energy
❷ Work done
SoluTion :-
☞ As we know that initial kinetic energy = ½ × mu²
➸ KE = ½ × 1.5 × 20²
➸ KE = 1 × 1.5 × 10 × 20
➸ KE = 300 J
➟Therefore, Initial kinetic energy = 300 Joule
☞ As we know that Final kinetic energy = ½ × mv²
➸ KE = ½ × 1.5 × 25²
➸ KE = ½ × 1.5 × 25 × 25
➸ KE = 468.75 J
➠ Therefore, Final kinetic energy = 468.75 Joule
➸ Total work = 468.75 - 300
➳ Total work = 168.75 J