The discussion revolves around calculating the momentum of a ball thrown vertically upward at different points in its trajectory, specifically at its maximum height and halfway to that height. The subject area includes concepts of momentum, kinetic energy, and projectile motion.
The discussion has progressed with participants providing hints and guidance on understanding kinetic and potential energy relationships. There is an ongoing exploration of how energy conservation applies to the problem, with some participants confirming calculations and others questioning assumptions about energy states.
Participants note that no calculations are required for certain points, and there is a focus on understanding the principles of energy conservation without needing to find the maximum height explicitly. The discussion reflects a mix of attempts to calculate and clarify concepts related to projectile motion.
This is just an example of projectile motion. If you wanted, you could figure out the height it reaches before falling back down. But you won't need that. Hint for (a): No calculation is required.mandy9008 said:how am I supposed to know the highest point?
Right.mandy9008 said:okay i got you, the momentum when it reaches the maximum height is zero.
Correct. Here you'll have to figure out the new speed. Hint: What happens to the kinetic energy?but this is not the case for it when it is halfway there, correct?
Neither. (But their sum remains constant.)mandy9008 said:Is it the potential energy or the kinetic energy that stays the same throughout?
You found the height reached and the original KE.mandy9008 said:so KE=mgh
v^2 = 2gh
12 m/s ^2 = 2 (9.8 m/s^s)h
h=7.35m
KE= (0.25kg) (9.8 m/s^2)(7.35m)
KE= 18.0 J
Good. Now use that to solve for the speed at that point. Then the momentum.mandy9008 said:KE= (0.25kg) (9.8 m/s^2)(3.675m)
KE= 9.00375 J
Sure, that works.mandy9008 said:KE= p^2 / 2m
9.00375J = p^2 / 2(0.25kg)
p=2.1218 kg m/s
is this correct?