 Which type of car, a heavier or lighter one, needs more force to slow down with the same deceleration?

› It is harder to slow a heavier car because of Inertia › Inertia is NOT a force, but a way to describe the movement of objects  Read the Introduction on Page 25

 This activity will depend on your observational skills and your ability to describe qualitatively what happens in the investigation.

 Lets Review the procedure 1-7.

 Using the materials provided, follow the procedure for Parts A and B.

When you are finished, Answer Analysis Questions 1-3 in your notebooks!

1.

A. Changes in direction and speed of marbles traveling inside the circular track: › Direction changed constantly because of the force the wall exerted on the marble. Similarly, the surface of the circular track rubbed on the marble and slowed it down slightly.

1.

B. Changes in direction and speed of the marbles when the traveled outside of the track: › › Once outside the track, the marble direction was a straight line, moving across the table.

The speed slowed slightly because of the table surface rubbing the marble Did Mass effect the marble?

• Once the marble left the track, the only force acting on it is friction, so its mass does not affect its motion!

 It will eventually stop. That means there must be some force acting on the marble, otherwise it would just continue to move in the straight line because of inertia.

 This force is FRICTION between the marble and the table, and the air and the marble.

 Without friction, the marble would continue on at a constant speed in a straight line forever (unless another force acted upon it)

A.

Opening position of the circular track: B.

› The marble left the opening in a different direction for each opening position. Once it left the circular track, however, it continued in a straight line.

Mass of the marble.

› When comparing the glass (lighter) marble to the heavier (metal) one, no changes occurred to the direction that the marble traveled.

3.

A.

B.

The car would take that path because of inertia, which in the absence of other forces keeps moving objects in a straight line C.

If the car had more mass, its direction would not change. It would, however, affect the force needed to stop the car.

 Think of a time you were in a car or go kart and you went around a sharp curve quickly.

 What did it feel like??

Your body felt pushed or pulled toward the outside of the curve, and you may have even slipped or bumped into the side of the car.

 When the car/kart turns suddenly, your body's inertia kept you going straight while the car turned.

 The driver of a lighter car can more likely avoid accidents because the car has less inertia, and therefore, its motion can be more easily changed.