Linear momentum handball problem

[beastysk8er]

Homework Statement

A handball of mass 0.10 kg, traveling horizontally at 30 m/s, strikes a wall and rebounds at 24 m/s. What is the change in the momentum of the ball?

Homework Equations

change in momentum = mv2 - mv1

The Attempt at a Solution

Do you take 24 as negative or positive? If you take it as neative you get -2.4-3=-5.4 if you take it as positive you get 2.4-3= -.60
both answers given in the problem are either positive 5.4 or positive 6.0. Thanks for your help

 

[Doc Al]

If you take the 30 m/s velocity as positive, then you'd better take the 24 m/s as negative since it's going in the opposite direction. For the final answer they just want the magnitude of the change in momentum, which is always positive.

 

[baba89]

!

I would approach this problem by first clarifying the direction of the velocity. In this case, since the handball is traveling horizontally, we can assume that the velocities before and after the rebound are in the same direction. Therefore, we do not need to consider the negative or positive sign when calculating the change in momentum.

Using the equation for change in momentum, we can calculate the change in momentum to be:

change in momentum = (0.10 kg * 24 m/s) - (0.10 kg * 30 m/s) = 2.4 kg*m/s - 3 kg*m/s = -0.6 kg*m/s

This means that the momentum of the handball decreases by 0.6 kg*m/s after rebounding from the wall. It is important to note that momentum is a vector quantity, meaning it has both magnitude and direction. In this case, the negative sign indicates that the momentum is in the opposite direction after the rebound.

I would also recommend checking the units of the final answer to ensure that it is in the correct units of kg*m/s. If the units are not correct, it could be an indication of an error in the calculation. Additionally, it is always good practice to include units in the final answer to avoid confusion.

I hope this helps clarify the solution to the problem. As a scientist, it is important to pay attention to details and make sure all variables and units are properly accounted for in order to arrive at an accurate solution.