# An assignment

1. Mar 25, 2007

### harmeet_angel

it's on centripetal force and gravitation problems..
wonderin if anyone can provide me answers such that i can compare mine
here's the assignment
http://www.geocities.com/cheemaharmeet/assignment.jpg

mine are {
1. 8N;
2. 1.97 hr;
3. 7.9E3 m/s
4. 382.26 m, 5.49E3 N
5. 8E-10 N
6. 2.93E41 kg}
I would really thankful, is someone can provide me answers..
and if u can do atleast.. please try #5.. i am confused over that.because my book also have answer to that question, and mine one's different from that

2. Mar 25, 2007

### hage567

Regarding #5, what is the answer the book gives? I think I know why you got a different answer.

Last edited: Mar 25, 2007
3. Mar 25, 2007

### harmeet_angel

thnx a lot for assuring me..
and for #4

N-W = centripetal force
m.(normal a)-mg = m(v^2/r)

but normal a=7g

so
(v^2/r)=7g-g

so r=(v^2/g)
=382.23 m

and
N = 7 x 9.81 x 80 kg

I think i am wrong, perhaps because in the question it says "acceleration of the pilot"..
so that means net acceleration?

4. Mar 25, 2007

### hage567

Note that I edited my first post about question #5. Can you tell me what the book's answer is?

5. Mar 25, 2007

### harmeet_angel

6.8 N
umm.. i think this isn't possible though

6. Mar 25, 2007

### hage567

Even if you do it this way, shouldn't it be 6g on the bottom (7g-g=6g)?

The wording is bit confusing in the question. I would think they are just asking for the acceleration, so then r = (v^2)/7g.
To find the force of the seat on the pilot, you just sum the forces up, so N - mg = mv^2/r. That's the approach I would take, but you decide what you want to do.

7. Mar 25, 2007

### harmeet_angel

oops, that was a typo
umm.. yea, i think your way''s right

8. Mar 25, 2007

### hage567

Is that supposed to be 6.8x10^-10 N though? Gravitational force is a vector. So for the third mass (4kg), you need to break up the force into its x and y components. Then do a sum of the forces in each direction. Then find the resultant of those two. Does that make sense? If you do that, you should get the answer the book gives.

9. Mar 25, 2007

### Nacer

Yes 6.8x10^-10 N is the correct answer for 5/.

Regards.

Nacer.