Final answer:
The product of force and the time interval over which it acts is known as an impulse, represented by J, and is directly related to the change in momentum of the object according to the impulse-momentum theorem.
Step-by-step explanation:
The product of the force and the time over which the force acts on an object (force x change in time) is called impulse. This is represented by the symbol J. Impulse is directly proportional to the change in momentum (Δp) of the object, which means the effect of a force on an object depends on how long it acts as well as the strength of the force. This relationship between impulse and momentum is encapsulated in what is known as the impulse-momentum theorem, which states that the impulse is equal to the average net external force multiplied by the time the force acts, and this equals the change in momentum (Fnet Δt = Δp).