It is not rare for any motion to change quickly. When playing sports you should expect motions to change quickly.
to change unless another force acts upon it
Motion is any movement or change. This can be position or time.
Acceleration
When neither of them had any motion to begin with. Hence, their motion remains constant, because they didn't have any to begin with.
Any change in motion (direction or speed) is a change in velocity.Velocity is a vector quantity which means that it has a magnitude and a direction.
Energy applied to it.
motion
Inertia
I think this question is not phrased very well. Any force can change objects velocity (speed+direction). If fact that is the definition of the force - F=ma any force, by definition itself, can change objects velocity. Maybe you meant what force can change objects direction of motion? In that case - any force that has a different direction (not the same as direction of motion) Any force can change an object's motion.
This is one definition of acceleration (including deceleration) - any change in the speed of motion of a moving object, or in the direction of its motion. Motion is a vector value with both speed and direction.
It means any change in -- speed -- direction -- or both. Constant or 'uniform' motion means steady speed in a straight line.
Any change in motion (direction or speed) is a change in velocity.Velocity is a vector quantity which means that it has a magnitude and a direction.