Science

Homework: Forces Name: _____________________ Section: ______

Copyright 2008 by S. Kanim, M. Loverude, and L.Gomez 1

1. For each situation below, draw a free-body diagram of the object that is identified. Label each force that you have included in your free-body diagram to indicate (1) the type of force, (2) the object on which the force is exerted, and (3) the object exerting the force. i. A block that is at rest on a ramp. ii. A block that is tethered by a string to a horizontal ramp.

The block is at rest, and there is no friction between the block and the ramp.

iii. The rag in the diagram. The window washer is using a stick to push the rag

upwards along the window.

2. A student has a weight of 750 Newtons. What is the mass of the student? Show your work.

3. What is the gravitational force exerted on a metal cube of mass 150 grams? Show your work.

θ

Block Ramp

µ = 0

String

Block θ

Stick

Rag

Window

Lab Homework 4: Forces

2

4. The massless string shown at right is wrapped around two

pulleys. It is tethered to the desk on one side and a mass hangs from the other side. Rank the tensions at the six labeled points along the string. Explain how you determined your ranking.

5. A person stands on a ladder that is resting against a wall. (Assume that there is no friction between the ladder and the wall.) Draw a free-body diagram of the ladder in the space to the right. Label each force that you have included as you did in question1. (Hint: The force on the ladder by the person is not a weight!)

6. In lab, you ranked the coefficients of friction for 3 carts

with different materials on the bottom: plastic, cork and fabric. In addition, you calculated the coefficient of kinetic friction for a cart with a cork bottom, and drew a free-body diagram for this cart as it was pulled at constant speed along a track. i. At right, draw a free-body diagram for the cart with the

fabric bottom as it slides at constant speed along the track. Sate how (if at all) this diagram is different from the one you drew for the cart with the cork bottom. Explain.

ii. Which forces in your free-body diagrams have the same

magnitude for the cork-bottomed and fabric-bottomed carts? Explain. iii. List all of the forces that are not the same for the two carts. For these forces, state which cart

has the larger force. Explain.

Pulley

Hook and slotted masses

Pulley

A

B

C D

E

F

Cart with masses

Track Force probe

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