Calculating Momentum and Speed in a Collision

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Homework Help Overview

The discussion revolves around a collision problem involving two trolleys with different masses and velocities. The original poster seeks to calculate the total momentum before the collision and the speed of the combined trolleys after the collision.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of momentum conservation principles and question how to derive the speed of the trolleys after they collide and stick together. There is also a focus on ensuring the correct interpretation of units and direction in the context of the problem.

Discussion Status

Some participants have confirmed the correctness of calculations regarding momentum and speed, while others are clarifying the implications of direction in the results. The conversation reflects a productive exploration of the problem without reaching a definitive conclusion.

Contextual Notes

There is an emphasis on understanding the definitions of momentum and the conditions of the collision, as well as the importance of units in the final answer. The original poster's question about part b indicates a need for further clarification on the application of the equations involved.

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Homework Statement



A trolley of mass 2kg, traveling at 3m/s, collides with a stationary 1kg trolley. If the trolleys stick together, calculate:
a) the total momentum before thecollision
b) the speed of the two trolleys arter th collision

Homework Equations



momentum = mass x velocity
momentum before collision or explosion = momentum after collision or explosion

a collision is where equal forces act in opposite directions. An explosion is when objects

The Attempt at a Solution




how do i get B?
 
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You get part b using the second equation.

Total momentum before collsion=total momentum after collision.

The fact that the cart sticks tells you what about their velocities after they collide?
 
if they collide and stick don't you add there masses to together so you have


2 x 3 = 2+1 x v

6 = 3 x v

6 / 3 = 2m/s

is that right?
 
is the answer the right units as well? I presume the direction is always written as positive in the outcome?
 
Yes, your answer is correct in magnitude and units. But direction is irrelevant--all they ask for is the speed, which is always a positive number (or zero!).
 

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