Calculating Momentum and Speed in a Collision

[thomas49th]

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?

 

[mbrmbrg]

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?

 

[thomas49th]

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?

 

[thomas49th]

is the answer the right units as well? I presume the direction is always written as positive in the outcome?

 

[Doc Al]

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!).