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I don't understand on how to solve all of these problems. I would-(Answered)

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I don't understand on how to solve all of these problems. I would like help on all of them please.?


Written Homework 7

 


 

Name:_______________________

 


 

This homework is due in class on 28 October, 2015. One section will be graded for 8 points.

 

The remaining 12 points will be awarded for completion.

 

In experiment 1, two hands push identical blocks of mass m

 

toward each other across a level, frictionless surface with a

 

constant force of magnitude Fo over the interval from t1 to t2.

 


 

Experiment 1

 


 

In this problem, you will consider 4 other experiments in

 

which the setup differs from that in experiment 1.

 


 

I.

 


 

m

 


 

m

 


 

In each experiment, both blocks start from rest at time t1 on a level, frictionless surface;

 

both hands exert the same magnitude force, Fo, over the interval from t1 to t2; and the

 

blocks do not run into each other during this interval.

 

In each experiment, consider the net work done during the interval from t1 to t2 by

 

external forces on the system that consists of the blocks and any spring or rod that may be

 

connecting them.

 

A. In experiment 2, the hands push in the same direction.

 


 

1.

 


 

2.

 


 

Experiment 2

 


 

Is the net external work on the system of the

 

two blocks in experiment 2, greater than,

 

less than, or equal to that in experiment 1?

 

m

 

m

 

Explain.

 

Is the net external impulse on the system

 

leftwards, rightwards, or zero? Explain. Compare it to that of Experiment 1.

 


 

B. In experiment 3, the blocks are connected by a spring. The Experiment 3

 

spring is initially neither stretched nor compressed.

 


 

1.

 


 

2.

 


 

Is the net external work on the system of the

 

two blocks and the spring in experiment 3

 

m

 

m

 

greater than, less than, or equal to that in

 

experiment 1? Explain.

 

Is the net external impulse on the system leftwards, rightwards, or zero?

 

Explain. Compare it to that of Experiment 1.

 


 

Physics 101 - David Kornreich - Ithaca College

 


 

Fall 2015

 


 

Written homework 7

 


 

Due: 28 October 2015

 


 

C. In experiment 4, the mass of one of the blocks is m/2.

 


 

1.

 


 

2.

 


 

Experiment 4

 


 

Is the net external work on the system of the

 

two blocks in experiment 4 greater than,

 

less than, or equal to that in experiment 1?

 

m

 

m/2

 

Explain.

 

Is the net external impulse on the system

 

leftwards, rightwards, or zero? Explain. Compare it to that of Experiment 1.

 


 

Experiment 5

 


 

D. In experiment 5, the blocks are connected by a rigid rod

 

(i.e., a rod that can not compress).

 


 

1.

 


 

2.

 


 

Rigid rod

 


 

Is the net external work on the system of the

 

m

 

m

 

two blocks and the rod in experiment 5

 

greater than, less than, or equal to that in

 

experiment 1? Explain.

 

Is the net external impulse on the system leftwards, rightwards, or zero?

 

Explain. Compare it to that of Experiment 1.

 


 

Physics 101 - David Kornreich - Ithaca College

 


 

Fall 2015

 


 

Written homework 7

 


 

Due: 28 October 2015

 


 

t = t1

 

II. Two identical blocks, A and B, on a frictionless surface are

 

connected by a spring of negligible mass. The spring is initially

 

unstretched. During the interval from t1 to t2, block A is pushed

 

through a distance dA by a hand exerting a force of magnitude

 

A

 

FA, as shown. Block B is held in place by a wall. The wall

 

exerts a force on block B that varies with time but is always

 

directed to the left. Consider rightwards to be the +x direction.

 

t = t2

 

A. During the interval from t1 to t2:

 

1. Is the work done on block A by the hand positive,

 

negative, or zero? Explain.?

 

?

 

?

 

?

 

?

 


 

The hand exerts

 

a constant force

 

of magnitude FA

 

B

 

dA

 


 

A

 


 

B

 


 

dA

 


 

2. Is the impulse done on block A by the hand positive, negative, or zero? Explain.

 


 

3. Is the work done on block B by the wall positive, negative, or zero? Explain.?

 

?

 

?

 

4. Is the impulse done on block B by the wall positive, negative, or zero? Explain.

 


 

5. Consider system ABS, which consists of block A, block B, and the spring. ?

 

Write an expression for the net external work done on system ABS by external forces in

 

terms of given quantities (i.e., FA, dA, t1, and/or t2). Explain.?

 

?

 

?

 

?

 

?

 

6. Explain why writing a similar expression for the net impulse would be much more

 

dif?cult.

 


 

Physics 101 - David Kornreich - Ithaca College

 


 

Fall 2015

 


 

Written homework 7

 


 

Due: 28 October 2015

 


 

B. Block B is now removed, so that the right end of the spring is

 

now directly in contact with the wall, as shown. During the t = t3

 

interval from t3 to t4, block A is again pushed a distance dA by

 

a hand exerting a constant force FA. The wall exerts a force

 

on the spring that varies with time but is always directed to

 

the left.

 


 

Let system AS consist of block A and the spring.

 

Consider the interval from t3 to t4:

 


 

The hand exerts

 

a constant force

 

of magnitude FA

 

A

 

dA

 


 

t = t4

 


 

1. Is the net external work and the net external impulse

 

done on system AS by external forces over this interval

 

greater than, less than, or equal to that on system ABS

 

over the interval from t1 to t2? Explain.

 


 

A

 

dA

 


 

2. Write an expression for the work done on block A by the hand over this interval in terms

 

of the given quantities (i.e., FA, dA, t3, and/or t4). Explain.

 


 

3. What is the displacement of the left end of the spring during this interval?

 


 

What is the displacement of the right end of the spring during this interval?

 

Which of these displacements should be used to calculate the work done on the

 

spring by the wall? Explain.

 


 

Is the work done on the spring by the wall positive, negative, or zero?

 


 

Physics 101 - David Kornreich - Ithaca College

 


 

Fall 2015

 


 

Written homework 7

 


 

Due: 28 October 2015

 


 

4. Write an expression for the net external work done on system ABS over this interval by

 

external forces in terms of the given quantities (i.e., FA, dA, t3, and/or t4). Explain.?

 

?

 

?

 

?

 

?

 

?

 

5. Explain why writing a similar expression for the net impulse would be dif?cult.

 


 

C. Is your answer for question B4 consistent with your answers for questions B1 and A3? If so,

 

explain how. If not, resolve the inconsistency.

 


 

Physics 101 - David Kornreich - Ithaca College

 


 

Fall 2015

 


 

 

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