Net Forces and Vectors AND LAB

Sigchi4life
Category:
Physics
Price: $20 USD

Question description

1.  Two ropes are attached to a wagon, one horizontal to the west with a tension force of 30 N, and the other east and at an angle of 30° northward and a tension force of 40 N. Find the components of the net force on the cart. Show all your work.

PICTURE

Answer:

2.  A 2.0 kg block rests on a level surface. The coefficient of static friction is µs = 0.60, and the coefficient of kinetic friction is µk = 0.40. A horizontal force, F, is applied to the block. As F is increased, the block begins moving. Describe how the force of friction varies as F increases from the moment the block is at rest to when it begins moving. Indicate how you could determine the force of friction at each value of F―before the block starts moving, at the point it starts moving, and after it is moving. Show your work.

Answer:

(8 points)


3.  A 12 kg barrel is pulled up by a rope. The barrel accelerates at 1.2 m/s2. Find the force exerted by the rope. Show all your work.

Answer:

Laboratory Instructions

Laboratory: Net Force

Materials

Supplied

Student Guide

Laboratory Guidelines

Graph Paper

scale, spring (10 N)

scale, electronic

ramp kit

slotted weight set, steel

protractor

ruler, metric

Also Needed

tape, masking

string

books

household objects – shoes, 2 kinds

Advance Prep (3 days)

Review the list of materials for the lab prior to the lesson, because there are several items that you must supply.

Safety

Review the Laboratory Guidelines before conducting the lab.

Experiment: Part 1 – Measuring Friction on a Horizontally Moving Object

Procedure

1.  Using the spring scale, measure the weight of each shoe in newtons and record it.

2.  Make an attachment point to the shoe. You can tie the shoelaces of the shoe together, place a loop of string through a shoelace hole, or attach a binder clip to the shoe and place a loop of string through the binder clip.

3.  Make a data table like the one below:

Trial

Weight (N)

Applied force (N)

Frictional force (N)

Coefficient of friction (μ)

Athletic:

Shoe alone

Shoe + 100 g

Shoe + 200 g

Shoe + 300 g

Shoe + 400 g

Dress or Dance:

Shoe alone

Shoe + 100 g

Shoe + 200 g

Shoe + 300 g

Shoe + 400 g

4.  Attach the athletic shoe to a spring scale.

5.  Slide the shoe horizontally across the floor at a constant velocity and note the reading on the spring scale. The reading on the spring scale should remain constant when the velocity is constant. (Remember to keep the spring scale and string at an angle of zero degrees).

6.  Repeat Step 5 two more times and record the average force in the Applied Force column.

7.  Place the 100 g mass inside the shoe, weigh the shoe, and record the weight in newtons. Then repeat
Steps 4–6.

8.  Repeat Steps 4–7 with each subsequent mass up to 400 g.

9.  Repeat steps 4–8 with the dress or dance shoe.

10.  Draw a free body diagram of the shoe being pulled across the table and label all the forces on the shoe.

11.  Use Newton’s laws to calculate the force of friction. Remember that the shoe is moving at constant velocity. How must the applied force compare to the force of kinetic friction?

12.  From the force of friction, calculate the coefficient of kinetic friction for each trial.

13.  Plot the force of friction vs. the weight for each trial of each shoe. You will have two lines on the same graph, one for each shoe. Calculate the slope of each line and write it down.

Experiment: Part 2 – Measuring the Frictional Force on an Object Moving on an
Inclined Plane

Procedure

1.  To make an inclined plane, place a book under one end of the board.

2.  Place the athletic shoe on the end of the board.

3.  Gradually raise the board to increase the angle of inclination until the shoe slides down the board at a slow, constant velocity.

4.  Once you achieve this angle, keep the board propped up to that height with additional books to measure the angle. Test it again to make sure that the shoe slides down with the same slow, constant velocity.

5.  Using the protractor, measure the angle of inclination of the board at the base and write it down.

6.  Repeat Steps 2–5 with the dress or dance shoe.

7.  Draw a free body diagram of the shoe on the inclined plane and label all the forces acting upon it.

8.  Calculate the coefficient of static friction for each shoe from the respective angle of inclination using the equation µs = tan q.


1.  In Part 1, did the force of friction on the shoe depend on the weight of the shoe? If the two are related, why are they? What is the slope of the line on the graph of force of friction vs. weight, and what does that number represent? Explain using your data.

Answer:

2.  Does an athletic shoe work better on a basketball court than a dress or dance shoe? Why or why not? Explain using data from Parts 1 and 2.

Answer:

3.  If you wanted the athletic shoe to slide faster on a surface, what might you do to the shoe? Provide at least two ways to make the shoe slide faster, and explain in terms of the force of friction and the coefficient of friction.

Answer:


Tutor Answer

(Top Tutor) Daniel C.
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School: Rice University
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