# ch 7.3 help ## ch 7.3 help

anyone have any clue?

guest07
Guest

## Re: ch 7.3 help

Question 2:
M1V1i+M2V2=M1V1f+M2V2f
Masses are equal, so:
M(V1i+V2i)=M(V1f+V2f)
Initial velocity of object 2 is zero, and because they are of equal mass, the final velocity of object 1 will be zero (think about it):
M(V1i)=M(V2)
Divide out the masses and find that... V1=V2.
Simply put, because the masses are equal, all of the velocity is transferred from the incident object to the target object. PEACE.

Guesto
Guest

## Re: ch 7.3 help

Question 4:
They give you the ratios of the velocities as V:
1/V gives you the ratio of the masses. Don't really know why.
So those are the easy ones anyone get the 1st or 3rd one?

Guesto
Guest

## Number one

Use the formula below and solve for h:
1/2 (m/m+M^2) * v^2=gh
h = (1/2 (m/m+M)^2 * v^2)/g

super Mo
Guest

## Re: ch 7.3 help

Number two keeps getting marked wrong on maple TA for me. Is it exactly the same as the velocity given, or what equations do you use to determine it?

blah
Guest

## question 2

I was getting it wrong too u have to add negative... So if velocity is 14.55 final ans is -14.55.

hwilson
Guest

## anyone got numbers 1, 2, 3, 4, with the correct signs?

i really need help with these

spetro71
Guest

## Q#3

Q#3
An object makes an elastic head-on collision with another "target" object which is initially at rest. If the ratio of incident mass over target mass is 0.5432 what is the velocity of the incident object after the collision in multiples of its incident velocity (see sheet 25,29)? Give the result with the appropriate sign taking the incident velocity as positive.

anybody has any idea how to do this question. thanks

p
Guest

## Re: ch 7.3 help

1, 2, 3 are all negative answers
4 is positive

However, I keep getting 4 wrong. any suggestions?

guestttt
Guest

## need help with # 3 and 4

anyone got any ideas

spetro71
Guest

## #3/4

I have tried everythign with these two problems. Can anyone offer any direction (that 1 over V thing is not working at all).

lanthony
Guest

## Question 3

Here's what I did
An object makes an elastic head-on collision with another "target" object which is initially at rest. If the ratio of incident mass over target mass is 0.7014 what is the velocity of the incident object after the collision in multiples of its incident velocity (see sheet 25,29) ? Give the result with the appropriate sign taking the incident velocity as positive.
You know the ratio is 0.7014, to keep things simple I said m1=0.7014 and m2= 1 since dividing m1/m2= 0.7014
v1=(m1-m2)/m1+m2)
v1=(0.7014-1)/1+0.7014)= -0.1755

Has anyone gotten 4?

student
Guest

## Question 4 Possible Solution

For number 4, did anyone just try using the value of the incident velocity. The reason I say this is because V1= (m2/m1)V2 +V1'....

I can't do it because my maple ta is down, but i'd love to know. S
Guest

## question 2

Does anyone know how to solve number two?
I've tried but I can't seem to get it....

Thank you!

stuckk
Guest

## Re: ch 7.3 help

For number 4 I used this:

2*(v2'/v1) - 1 = m1/m2

Seems to work.

guest3
Guest

## Q 2

use the equation

0.5((bulletmass/(bulletmass+woodmass))^2*velocity^2=g*h

divide the bullet mass by the bullet mass plus the wood's mass, square it then multiply by 1/2. square the velocity and multiply that by your current ratio. Then divide by 9.81 to get your height.

student
Guest

## Re: ch 7.3 help 