# Help With Physics Homework

## Homework Statement

Please be advised, i posted these questions on two other forums, so you may check to see if a question you're planning on answering has been addressed. so far, (4.9) has been answered, i will try to keep you up-to-date

http://www.mathhelpforum.com/math-help/urgent-homework-help/20141-jhevon-needs-help-physics.html

http://www.artofproblemsolving.com/Forum/viewtopic.php?p=941182#941182

there are quite a few questions, any help is appreciated:

4.9)

A 0.140 kilogram baseball traveling 35.0 m/s strikes the cather's mitt, which, in bringing the ball to rest, recoils backward 0.11 meters. What was the average force applied by the ball on the glove?

4.25)

One 3.20 kilogram bucket is hanging by a massless cord from another 3.20-kilogram bucket, also hanging by a massless cord. (a) is the buckets are at rest, what is the tension in each cord? (b) If the two buckets are pulled upward with an acceleration of 1.60 meters per second squared by the upper cord, calculate the tension in each cord.

4.54)

A roller coaster reaches the top of the steepest hill with a speed of 6.00 kilometers per hour (1.67 meters per second). It then descends the hill, which is at an average angle of 45.0 degrees and is 45.0 meters long. What is its speed when it reaches the bottom? Assume the kinetic coefficient of friction is 0.18.

5.15)

How many revolutions per minute would a 15-meter-diameter Ferris wheel need to make for its passengers to feel "weightless" at the topmost point?

5.37)

A typical white dwarf star, which was once an average star like our sun but is now in the last stage of its evolution, is the size of our moon but has the mass of our sun. What is the surface gravity on this star?

5.48)

During an Apollo lunar landing mission, the comman module continued to orbit the moon at an altitude of about 100 kilometers. How long did it take to go around the moon once?

## Homework Equations

i have no idea, i am asking these questions on behalf of my cousin who does not have access to a computer at the moment

## The Attempt at a Solution

like i said, i don't even do physics, so i don't have any attempts. all i can say is that for the first question i was thinking of using the suvat equation v^2 = u^2 + 2as to find the acceleration and then use F = ma to find the force. but the numbers don't seem right to me

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PhanthomJay
Homework Helper
Gold Member
Your attempt at the first problem looks good. You get large accelerations when the speed changes over a very brief time interval.

Your attempt at the first problem looks good. You get large accelerations when the speed changes over a very brief time interval.
thank you for your response (do they have a thanks button or anything here?). i don't know. the answer i got was 779.5 (kg*m)/(s^2). that seems weird. i guess the problem here is the time interval, but how do i figure that out?

what are the relevant equations for the rest of the questions? i don't need someone to do the problems for me, providing relevant formulas and hints in the right direction are enough, thanks

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the problems were addressed here for those of you who are interested