The tenancy of a moving object to continue moving in a strait line or a stationary object to remain in place is called

The tendency of a moving object to continue moving in a straight line or a stationary object to remain in place is called inertia.

According to law of inertia, an object maintains its state of rest or motion unless acted upon by an external force. an object can not move on its own unless force is applied on it to move it. also an object can not come to stop on its own unless acted upon by an external force to stop it. This is also known as newton's first law.