certain force acting on 20 kg mass changes its velocity from 5m/s to 2m/s .calculate the work by the force
Answers
Answer:
Given:
Mass of object = 20 kg
Initial velocity = 5 m/s
Final Velocity = 2 m/s
To find:
Work done by the force.
Concept:
As per work - energy theorem, work done by any force is equal to change in kinetic energy.
W = ∆KE
Calculation:
Initial KE = ½mv²
=> Initial KE = ½ (20)(5)²
=> Initial KE = 250 Joules...(KE1)
Final KE = ½m(v')²
=> Final KE = ½(20)(2)²
=> Final KE = 40 Joules....(KE2)
Hence, Work done = ∆KE
=> Work = KE2 - KE1
=> Work = 40 - 250
=> Work = -210 Joules.
Negative work done refers to the fact that force applied actually decreased the velocity of the body.
Given:
Initial velocity = 5 m/s
Final velocity = 2 m/s
Mass of body = 20kg
To find: We have to find the work done by the force from the given condition.
Solution:
We know that, Work done by a force is equal to it's kinetic energy.
i.e. Work = Kinetic Energy
We will now find the initial kinetic energy and final kinetic energy.
Initial kinetic energy = 1/2 mv²
= 1/2 (20) × (5)²
= 10 × 25
= 250
Therefore, Initial kinetic energy = 250 Joules --------- (i).
Final kinetic energy = 1/2 mv²
= 1/2 (20) × (2)²
= 10 × 4
= 40
Therefore, Final kinetic energy = 40 Joules ------------ (ii).
Form (i) and (ii),
Total Kinetic energy / work done = 40 - 250
= -210