# Angular momentum and change in velocity

• physgrl
In summary, the turntable has a moment of inertia of 2.5 x 10-2 kg m2 and is spinning at 33.3 rev/min. A 0.25 kg ball of putty is dropped 0.20 m from the center of the turntable. Using the equations L=Iω and L=r*p, the new angular speed of the system can be calculated by setting the initial angular momentum equal to the final angular momentum, giving the equation Iω = (I+mr)ω(final). After correcting for the units, the calculation results in a new angular speed of 24 rev/min, as confirmed by the answer key.

## Homework Statement

A turntable has a moment of inertia of 2.5 x 10-2 kg m2 and spins freely at 33.3 rev/min. A 0.25 kg ball of putty is dropped vertically on the turntable at a point 0.20 m from the center. What is the new angular speed of the system?

a. 41 rev/min
b. 24 rev/min
c. 33 rev/min
d. 27 rev/min

L=Iω
p=mv
L=r*p

## The Attempt at a Solution

i tried to do Iω=(I+mr)ω(final)
i got 27 rev/min
the real answer is supposed to be 24rev/min according to the answer key

physgrl said:

## Homework Statement

A turntable has a moment of inertia of 2.5 x 10-2 kg m2 and spins freely at 33.3 rev/min. A 0.25 kg ball of putty is dropped vertically on the turntable at a point 0.20 m from the center. What is the new angular speed of the system?

a. 41 rev/min
b. 24 rev/min
c. 33 rev/min
d. 27 rev/min

L=Iω
p=mv
L=r*p

## The Attempt at a Solution

i tried to do Iω=(I+mr)ω(final)
i got 27 rev/min
the real answer is supposed to be 24rev/min according to the answer key

Can you show the details of your calculation? We can't tell you what you did wrong if you don't show us your work!

"i tried to do Iω=(I+mr)ω(final)"

Careful, mr does not have same units as I.

Yeah that was my error thanks!