Homework Help: Physics

Posted by Priyanka on Sunday, March 18, 2012 at 4:02am.

A 44.0-kg woman stands at one end of a 148 kg raft that is 6 m long. The other end of the raft is 0.5 m from a pier.

(a) The woman walks toward the pier until she gets to the other end of the raft and stops there. Now what is the distance between the raft and the pier? in m please

(b) How far did the woman walk (relative to the pier)? in m please

I tried the following:

(44*5)+(148*0.5)/(44+148) but i get the wrong answer I don't know what I am doing wrong! And for b I don't know how to do that! Please help am confused! Thank you.

Physics - drwls, Sunday, March 18, 2012 at 9:11am
They want you to neglect friction between the boat and the water. With that assumption, the center of mass of the boat and woman remain in the same place, relative to the pier. When she stops walking, the boat stops moving.

Let X be the distance of the close end of the boat from the pier. Initially
X = Xi = 0.5 m. Afterwards, X = Xf. You want to know the value of Xf.

Initial CM location =
[148*3.5 + 44*6.5]/(148+44) = 4.188 m

Final CM location =
[148*(3+Xf) + 44*Xf]/192 = 4.188

Solve for Xf
804= 444 + 148 Xf + 44 Xf
360 = 192 Xf
Xf = 1.875 m

The boat ends up farther from the pier, although the woman ends up closer to it.

(b) The woman was initially 6.5 m from the pier and ended up 1.875 m away. She moved 4.625 m closer, relative to the pier.
Physics - Priyanka, Sunday, March 18, 2012 at 12:57pm
Thank you Drwls! I really appreciate your help.

Answer this Question

Related Questions

physics - A 55-kg woman contestant on a reality television show is at rest at ...
Physics - A 220 kg wooden raft sits on a lake. When a 75 kg man stands on the ...
physics - A 5 m by 9 m raft whose mass is 18000 kg floats in fresh water. A 8590...
Physics - A 60.0 kg girl stands up on a stationary floating raft and decides to ...
Physics - A 60.0 kg girl stands up on a stationary floating raft and decides to ...
College Physics - One end of a 14 m long wire having a total mass of .8000 kg is...
Physical Science - A wooden raft 3 m long x 2 m wide x 20 cm thick floats on a ...
Physical Science: PLEASE HELP!!!!! - A wooden raft 3 m long x 2 m wide x 20 cm ...
Physics - A man of mass 65.2 kg stands on a scaffold supported by a vertical ...
Physics Help NOW! - A 64 kg woman stands on a very light, rigid board that rests...

For Further Reading

First Name:
School Subject:
Answer: