Conceptual Questions – Newton’s 1st Law
1. An object experiences two forces. One force is 3N downwards and the other is 3N upwards. According to Newton’s 1 st
law
1. the object is stationary
2. The object is not accelerating
3. the object has no mass
Explain why you chose your answer and why the other two are incorrect
2. When you are a rider in a car without your seat belt and the driver makes a sharp turn, you appear to slide towards
the side of the car. Use Newton’s 1st law to explain why you slide towards the door
3. You are in an automobile cruising at 35 miles/hr. You toss a tennis ball up in the air (inside the car). Where does it land
and why? Where would the tennis ball land if the driver brakes while the ball is in the air?
4. Your car is at rest. Suddenly you push down on the accelerator and the car accelerates forward. You feel that you are
pushed back into your seat. What is going on? Use Newton’s 1st law to explain.
5. Consider a book on top of a level table while the book is being pressed straight down by a hand.
a. Draw and label a FBD for the book
b. Is the magnitude of the weight equal to the magnitude of the normal force exerted by the table on the book?
Explain
c. How do the forces exerted on the book in this case compare to the forces exerted on the book when the hand
is not pushing? List any forces that are the same (i.e. same type of force, same direction, and same magnitude) in both
cases. Make a separate list of forces that change (or are not present ) when the hand is pressing down on the book.
6. A chain is suspended by a rope as shown at right. The chain is composed of four identical links and does not move.
a. In the spaces below, draw and label a free body diagram for each of the four links.
b. Rank from largest to smallest, the magnitudes of all forces on your diagrams. Explain your reasoning.
7. Let S12 represent the system consisting of links 1 and 2 of the chain in the problem 6 (i.e. treat links 1 and 2 as a single
object)
a. Draw and label a FBD for system S12
b. Compare the forces that appear on your FBD for system S12 to those that appear on your diagrams for links 1 and 2 in
problem 6
i. For each of the forces that appear on your diagram for system S12, list the corresponding force (or forces) on
your diagrams for link 1 and 2.
ii. Are there any forces on your diagrams for link 1 and 2 that you did not list? If so, what characteristic do these
have in common that none of the others share.
c. Let C represent the system consisting of the whole chain. Draw and label a FDB for C. Make sure that your diagram is
consistent with the reasoning you used in part b.
8. The FBD’s below show a force or forces acting on an object. Draw and label one more force (one that is appropriate to
the situation) that will cause the object to be in equilibrium.
9. If you know all of the forces acting on a moving object, can you tell in which direction the object is moving? If the
answer is yes, explain how. If the answer is no, give an example.
10. A hollow tube forms three quarters of a circle. It is lying flat on a table. A ball is shot
through the tube at high speed. As the ball emerges from the other end, does it follow path
A, path B, or path C? Explain your reasoning using Newton’s 1st law