Kinetics of a Particle

Now, suppose the observer is sitting in the particle, itself. For him the particle is not moving, but he is seeing that the particle is being pulled by a force T. Thus he will feel that there is an outward force that is balancing the force. The fictitious outward force is called inertial force.

One example:

A crate of mass M rests on a cart of mass m. The coefficient of friction between the crate and cart is and between cart and the road is . If the cart is to be pulled by a force P, such that crate do not slip, determine: (a) the maximum allowable magnitude of P and (b) the corresponding acceleration of the cart.