How to calculate increase in kinetic energy due to acceleration?

[ingram010]

Hi all

Hope some one can help with this

Calculate the increase in kinetic energy due to acceleration?

0.6m diameter Solid cylinder with a mass of 120kg, initial velocity of 20.94 rad/s and final velocity of 146.61 rad/s.

I have found an equation for the kinetic energy lost at impact:-

1/2 moment of inertia x initial velocity^2 + 1/2 moment of inertia x final velocity^2

My question is, am I right in thinking it is the same equation but I subtract one from the other in stead of adding them?

so

I = 1/2 mass x radius ^2

1/2 (5.4)(146.61)^2 - 1/2 (5.4)(20.94)^2 = 56851 Joules


Kindest regards

John

 

[WatermelonPig]

Assuming the cylinder is undergoing pure rotation, K = 0.5I(omega^2)
The change in kinetic energy is then 0.5I(omegafinal^2-omegainitial^2)
For a cylinder, I = 0.5M(R^2)
So (deltaK) = 0.25M(R^2)(omegafinal^2-omegainitial^2)
= 0.25(120)(0.3^2)(146.61^2-20.94^2) = 56851.22295J
So your answer is correct.