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Number 41. n and Collisions > Problems and Conceptual Exercises u=0 4m 2m The mo

ID: 1583270 • Letter: N

Question

Number 41.

n and Collisions > Problems and Conceptual Exercises u=0 4m 2m The most massive cart has an initial speed of vo; the other two carts are at rest initially. All carts are equipped with spring bumpers that give elastic collisions. (a) Find the final speed of each cart. (b) Verify that the final kinetic energy of the system is equal to the initial kinetic energy. (Assume the air track is iong enough to accommodate all collisions.) 41·.. An air-track cart with mass m 0.25 kg and speed uo = 1.2 m/s approaches two other carts that are at rest and have masses 2m and 3m, as indicated in Figure 9- 290. The carts have bumpers that make all the collisions elastic. Find the final speed of each of the carts, assuming the air track extends indefinitely in either direction. Figure 9-29 Problem 41 0 u=0 2m 3m Section 9-7 Center of Mass 42. CE Predict/Explain A stalactite in a cave has drops of water falling from it to the ually sp The drops an

Explanation / Answer

Given

m = 0.25 kg , v0 = 1.2 m/s

the collision is elastic collison

by conservation of momentum before and after collision the momentum is same

the mass m comes to rest after the collision , 2m starts to move

m*v0 = 2m*v

v = m*v0/2m = v0/2

v = 1.2/2 = 0.6 m/s

and

second case the conservation of momentum

the mass 2m comes to rest after the collision , 3m starts to move

2m*v0/2 = 3m*v

v = v0/3

v = 1.2/3 = 0.4 m/s