Identify the best definition of energy?
No work is done by a force on an object if
a) force is always perpendicular to its velocity
b) the object is stationary but the point of application of force moves on the object
c) the object moves in such a way that the point of application Of the force also moves
d) the force is always perpendicular to its acceleration.
An object of mass 1kg was moving at a speed of 10 ms−1. A constant force acts for 4s on the object and the speed of object becomes 2 ms−1 in opposite direction after the application of force. The force acting on the object have: