Work and Energy — Important Questions

A force must act on the object, The object must be displaced, The displacement must be in the direction of force

For work to be done, three conditions must be met: (1) A force must act on the object, (2) The object must be displaced, and (3) The displacement should have a component in the direction of the applied force. The magnitude of force or weight of object doesn't determine whether work is done or not.

80 J

Kinetic energy = ½mv² = ½ × 10 kg × (4 m/s)² = ½ × 10 × 16 = 80 J. Remember to square the velocity and multiply by half the mass.

Mass of the object, Height of the object, Acceleration due to gravity

Gravitational potential energy is given by PE = mgh, where m is mass, g is acceleration due to gravity, and h is height. It does not depend on velocity (that's for kinetic energy) or physical properties like color.

Neither kinetic nor potential energy

An object at rest has no kinetic energy (since velocity = 0) and no gravitational potential energy if it's on the ground (since height = 0). However, it may still possess other forms of energy like chemical energy.