A. The gravitational force exerted by the Sun on the Earth holds the Earth in an

Question

A. The gravitational force exerted by the Sun on the Earth holds the Earth in an orbit around the Sun. Let us assume that the orbit is perfectly circular. The work done by this gravitational force during a short time interval in which the Earth moves through a displacement in its orbital path is:

1. zero.

2. positive.

3. negative.

4. impossible to determine.

B. A dart is inserted into a spring-loaded dart gun by pushing the spring in by a distance x. For the next loading, the spring is compressed a distance 2x. How much work is required to load the second dart compared with that required to load the first?

1. four times as much

2. two times as much

3. the same

4. half as much

5. one-fourth as much

C. A dart is inserted into a spring-loaded dart gun by pushing the spring in by a distance x. For the next loading, the spring is compressed a distance 2x. How much faster does the second dart leave the gun compared with the first?

1. four times as fast

2. two times as fast

3. the same

4. half as fast

5. one-fourth as fast

Explanation / Answer

A) 1

Gravitational force is always perpendicular to the direction of motion . So theta= 90 degree

W= Fd cos theta = 0

B)1

W is directly proptional to x^2

So if distance is doubled work will increase 4 fold.

C) 2

.5 mv^2 = .5 k x^2

V = x (k/m)^.5

So if x is doubled velocity will also get doubled.

Please let me know if it was helpful. Thank you

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