# Hey all, I really need help with this homework. Any help would be appreciated

Hey all, I really need help with this homework. Any help would be appreciated(FIXED)

Problem: Ball of mass m hangs on a string of length L straight down from a cart of mass
M standing on horizontal rails. The cart can move along the rails without friction.
While the cart is at rest, the ball is given a horizontal velocity v0, v0 < sqr(2gl) directed
along the rails.

(a) What is velocity of the ball when it reaches
its maximal elevation?
(b) What is elevation h that the ball reaches
above its original location?

First of all hello.
I am new to this forum and don't really know your ways yet, so please forgive me if I do something wrong. This problem has tormented me for days. I did all the other homework problems for this week and this is the last one. If anyone would help me solve the problem I would be forever grateful.

m = mass of the ball
M = mass of the cart
v0 = velocity given to the ball
V = velocity of the cart
theta = angle between the starting position of the string and the maximal elevation of the string

Sorry for not giving any attempts, but I really don't know where to start on this one. All i have is:
(1/2)m(v0)^2 = (1/2)mv^2 + mgh + (1/2)MV^2
mv0 = mvcos(theta) + MV
I also found center of mass, in respect to the position of the ball:
(L - mL/(M + m) = CM

Last edited:

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SammyS
Staff Emeritus
Homework Helper
Gold Member
1. Ball of mass m hangs on a string of length  straight down from a cart of mass
M standing on horizontal rails. The cart can move along the rails without friction.
While the cart is at rest, the ball is given a horizontal velocity v0, v0 <
p
2g, directed
along the rails.

## Homework Equations

(a) What is velocity of the ball when it reaches
its maximal elevation?
(b) What is elevation h that the ball reaches
above its original location?

First of all hello.
I am new to this forum and don't really know your ways yet, so please forgive me if I do something wrong. This problem has tormented me for days. I did all the other homework problems for this week and this is the last one. If anyone would help me solve the problem I would be forever grateful.

Hello spartanpo. Welcome to PF !

You have some typos.

I am unable to make sense of your question.

DaveC426913
Gold Member
I am new to this forum and don't really know your ways yet
Well, our ways are that you must show your attempts to solve the problem before we can help.