- #1

Puddles

- 12

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## Homework Statement

[/B]

(a.)Apply the law of conservation of momentum to the perfectly inelastic collision of a moving object of mass m1 and velocity vi with a stationary object of mass m2

(b.) Solve this for final velocity vf

(c.) Write a formula for the initial kinetic energy (KEi)

(d.) Write a formula for the final kinetic energy (KEf) in terms of vf

(e.) Substitute your formula for vf from (a.) into your equation above to get a formula for KEf in terms of m1, m2, and vi alone

(f.) Find the ratio KEf/KEi in terms of m1 and m2 alone

(g.) Express the final kinetic energy in terms of the initial kinetic energy KEi

(h.) For the case of a moving object much, much more massive than the stationary object (m1 >> m2), how much kinetic energy is lost in the collision?

(i.) For the case of a stationary object much, much more massive than the moving object (m2 >> m1), how much kinetic energy is lost in the collision?

(j.) Given two projectiles fired with the same KE, fired at a target which is free to move, which will cause the most destruction (that is, result in the greatest loss of kinetic energy), a small high-speed projectile or a massive slow-moving one?

## Homework Equations

Momentum: P = m x v

Kinetic Energy: KE = 1/2mv^2[/B]

## The Attempt at a Solution

(a.) P = M1V1 + M2V2 = (M1+M2)Vf

(b.) Vf = M1V1/(M1+M2)

(c.) Cons. Energy, KEi = KE1 + KE2, KEi = 1/2(M1V1^2) + 1/2(M2V2^2)

KEi = 1/2(M1V1^2)

(d.) 1/2 (M1 + M2) Vf^2

(e.) Here's where my confusion starts, (M1+M2)Vf = M1V1 + M2V2 and 1/2(M1+M2)Vf^2, I tried

1/2(M1+M2)((M1V1+M2V2)/(M1+M2))^2, substituting in for Vf but I'm not sure if that's right

(f.) I'm not even sure how to resolve this from the last piece of information, because I can't set M1 and M1 or M2 and M2 equal to each other from my previous formulas, can I?

Since I'm stuck there I couldn't make an attempt on the rest yet.