Chapter 8, Problem 5A

When the force of impact on an object is extended in time, does the impulse increase or decrease?

To determine

To identify: Whether the impulse will increase or decrease, when force of impact on an object is extended in time.

Answer to Problem 5A

The impulse increases with extension of time of the force of impact.

Explanation of Solution

Introduction:

When a very large force or impact acts upon a body for a very short duration, the effect of the force along with time need to be considered as a whole. This product gives the parameter impulse.

Based on the force F applied on a body for a particular duration t, the impulse can be expressed as,

  $\text{Impulse}=Ft$

The above equation suggests that under a constant force, impulse and time follow a direct relationship and hence it increases when time of impact is increased.

However, one aspect to be considered is that, in cases when the force of impact decreases as the time is increased, the impulse remains fairly constant. An example of this situation is during collisions. To minimize the impact of a force, the time of collision is extended. A real-world application of this is in the case of airbags in cars, which are provided to increase the time of impact of the accident so that less force is experienced by the person inside the car.