A body of mass 1 kg is moving with a velocity of 10 m/s. A constant force acts on it for 4 seconds, increasing its velocity to 20 m/s. The work done by the force over this period is:
NEET - 2015
The work-energy theorem for constant force is derived from:
Conservation of momentum
Newton's Second Law (F = ma) combined with kinematics (v² − u² = 2as)
Conservation of energy
Newton's Third Law
For 3-dimensional motion under constant force, the work-energy theorem is obtained by:
Using conservation of momentum in 3D
Using v² − u² = 2a·d (vector form), then multiplying by m/2 to get F·d = ΔKE
Using v² − u² = 2as in x-direction only
Integrating Newton's 2nd Law over time