Velocity and Loss in Energy onedimensional

AI Thread Summary
A 15kg object dropped from a height of 11.58m experiences a loss of energy of 320 J, leading to a calculation of its velocity upon entering a container. The gravitational potential energy (GPE) is calculated as 1702.26 J, and after accounting for the energy loss, the remaining energy is 1382.26 J. This energy is then equated to kinetic energy (KE) to find the velocity, resulting in a value of approximately 13.57 m/s. There is confusion regarding the energy loss, which is suggested to be due to friction, as the object should ideally convert potential energy to kinetic energy without loss. The discussion highlights the importance of understanding energy transformations in physics problems.
Nuingaer
Messages
1
Reaction score
0

Homework Statement


If a 15kg object is released from a height of 11.58m and the objects loss in energy is 302 J, determine its velocity as it enters the container (object is being dropped straight down into a container)
Assume g = 9.8m/s^2
m(object) = 15kg = w(object) = 147N
s = 11.58m
ΔE = -320 J

Homework Equations


Had no idea. But the ones i know that i thought could apply:
ΔKE = KE(final) - KE(initial)
KE = 1/2 * mv^2
GPE = mgh
v^2 = u^2 + 2as

The Attempt at a Solution


Okay, I had no idea how to do this, but i tried to work out as many things as i can then mash em together to get an answer :p

GPE = mgh
=15*9.8*11.58
=1702.26

Then i thought; well if the loss in energy is 320 J then i could take that from the original GPE
1702.26 - 320 = 1382.26 J

and now i could work out the new height by subbing it back in
1382.26 = 15*9.8*h
h=9.403m

And here is where it gets iffy... they say the velocity when it enters the container, but the container isn't at 9.403m its at 0...right? that's what i got from the question anyway. Therefore how did they only lose 320N? So I assumed that I could say its KINETIC energy is the 1382.26 J, and the height of the container is the difference because they say when it "enters".
Therefore..
KE = 1/2 * m * v^2
1382.26 = 1/2 * 15 * v^2
2764.52 = 15 * v^2
v^2 = 184.30
v = 13.58 m/s

We don't have the answer to this question yet, but *a lot* of other people got 13.66m/s as the answer... so since i had no idea how to do this question and no basis to support whether I am right or not, could someone help me out and either point out where i went wrong or if I'm right? thank you!
 
Last edited:
Physics news on Phys.org
I think they mean by lose of energy that it's due to friction, because when dropping an object from a certain hight the object does't lose energy but the energy is converted from potential to kinetic, and so when the question states that there there was loss in energy i think its due to friction(i might be wrong i don't know). If this is the case then i think you should do this:
Energy (at h=11.58 )-Energy lost=1702.26-320=1382.26
Ek=1/2*mv^2
v=13.57m/s
in this case you take the barrol at hight 0.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top