Question

Argelia has a stack of schoolbooks sitting in the backseat of her car. When Argelia makes a sharp right turn, the books slide to the left of the seat until they come to a rest against the car door. Explain why this happens.

Answer 1

Answer:

Sample Response: Before making the right turn, the books were moving in a straight line. As the turn was being made, the books continued moving in a straight line due to inertia. The books slid across the seat until the car door exerted a force on them that caused them to make the turn with the rest of the car.

Answer 2

Answer:

The books slide to the left due to inertia, and then they come to a rest due to the force applied by the car door.

Explanation:

The entire motion of the books can be explained by using the first two laws of Newton:

- 1st Newton's law (also called Law of Inertia): an object at rest stays at rest and an object in motion stays in motion with constant velocity if no unbalanced forces act on it

- 2nd Newton's law: when an object is acted upon unbalanced forces, an acceleration is induced in the motion of the object, according to the equation

$F=ma$

where F is the net force on the object, m is its mass and a is its acceleration.

Coming back to our problem:

- At the beginning, Argelia makes a sharp turn right. Due to the law of inertia, the books (which are not fixed to the car) continue their motion straight as it was before the curve: so, since the car is moving right, they appear to go the left of the car.

- When the books hit the car door, they stop moving due to the 2nd Newton's law: in fact, the car door applies an unbalanced force against the books, and as a result the books have a negative acceleration (=deceleration), so they slow down and eventually they stop.