- #1
stacope32
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Homework Statement
A block of 55 g is sliding down a ramp of 35 degrees of inclination.The hypotenuse of the ramp is 63 cm and the height is 36 cm. vi = 0 as the block starts at rest.
Homework Equations
vf = vi + a(t)
d = vi*t + (a(t)^2)/2
kinetic energy = (mv^2)/2
The Attempt at a Solution
I did 3 trials of letting the block slide down the ramp and the time intervals I got each are:
1) 0.41 s
2) 0.44 s
3) 0.47 s
So then I used the d = vi*t + (a(t)^2)/2 formula to calculate the acceleration of the block and I got
1) 7.5 m/s^2
2) 6.5 m/s^2
3) 5.7 m/s^2
Then, I used the vf = vi + a(t) to find the velocity at the bottom of the ramp.
1) 3.1 m/s
2) 2.9 m/s
3) 2.7 m/s
And then I found the total energy at the top of the ramp , which would only be the potential energy as initial velocity is zero. So it's 0.19J that I calculated.
Then when I move to solve the total energy at the bottom of the ramp, there is a problem. Potential energy is zero and there's only kinetic energy, and also final energy should be smaller than initial energy because of friction, but I keep getting a greater value for all of them, as well as my change in mechanical energy, which should be negative and I keep getting a positive value. Please help.
initial energy 0.19 J
final energy (3 trials) calculated by (mv^2)/2
1) 0.26 J (it's greater that EI but should not be!)
2) 0.23 J
3) 0.2 J
*my teacher said that I should be getting a negative value for change of energy and she hasn't taught us how to do include experimental errors..she said the errors shouldn't affect the results like that so there must be something wrong with my process, but I can't figure out what it is?