Chapter 4, Problem 65A

(a)

To determine

Thecause of the occurrence of whiplash using Newton’s laws.

Explanation of Solution

Introduction:

Newton’s First Law of Motion: As per Newton’s First Law of Motion, an object remains in its state of rest or in motion until an external force acts on it. Whiplash is a serious neck injury of the person in the car when the car is struck from behind; the occurrence of whiplash can be explained using Newton’s Law of Motion.

Consider a person is sitting inside a car. The car seat supports the entire body of the person except for his head. When the car is suddenly struck from behind, thecar will accelerate in the forward direction.

Apply Newton’s First Law of Motion,

The seat accelerates the person’s body (except the head) in the forward direction.

As the head is not supported by the seat, it remains in its state of rest. The neck has to accelerate the head resulting in a serious neck injury.

(b)

To determine

The way headrest reduces the whiplash.

Answer to Problem 65A

The headrest reduces the whiplash as the seat accelerates the entire body of the person in the forward direction when the car is struck from behind.

Explanation of Solution

Introduction:

Newton’s First Law of Motion: As per Newton’s First Law of Motion, an object remains in its state of rest or in motion until an external force acts on it. Whiplash is a serious neck injury of the person in the car when the car is struck from behind; the occurrence of whiplash can be explained using Newton’s Law of Motion.

Consider a person is sitting inside a car. When the headrest is provided, the car seat supports the entire body of the person including the head. When the car is suddenly struck from behind, the car will accelerate in the forward direction.

Apply Newton’s First Law of Motion, the seat accelerates the person’s entire body including the head in the forward direction. Hence, this will prevent the person to suffer from a serious neck injury (whiplash).

Conclusion:

Thus, the headrest reduces the whiplash as the seat accelerates the entire body of the person in the forward direction when the car is struck from behind.