- #1

- 3

- 0

Relevant equations (I think...):

I=1/2MR^2

FR=Iα

α=a/R

So far, I have:

FR=Iα

FR=1/2MR^2(a/R)

F=1/2Ma

a=2*F/M=3.33333 m/s^2

and then,

v^2=2*a*6m, since initial velocity is 0.

v=7.26 m/s

But this is wrong, and I'm not sure why. Please help!

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- Thread starter atlarge
- Start date

- #1

- 3

- 0

Relevant equations (I think...):

I=1/2MR^2

FR=Iα

α=a/R

So far, I have:

FR=Iα

FR=1/2MR^2(a/R)

F=1/2Ma

a=2*F/M=3.33333 m/s^2

and then,

v^2=2*a*6m, since initial velocity is 0.

v=7.26 m/s

But this is wrong, and I'm not sure why. Please help!

- #2

gneill

Mentor

- 20,925

- 2,866

- #3

- 3

- 0

I'm so frustrated :)

- #4

gneill

Mentor

- 20,925

- 2,866

I'm so frustrated :)

mg and the normal force are equal and opposite, so their contribution vanishes. You only have to deal with the force applied via the string.

- #5

- 3

- 0

Answer is:

F=ma

35N=(21kg)a

a=1.667 m/s^2

v^2=0 + 2(1.667)(7.9), 0 being the initial velocity

v=5.1 m/s

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