- #1

suspenc3

- 402

- 0

r=0.2m

I=0.05kg(m^2)

m=2kg

P=3.0N

[tex]T = rFsin \theta[/tex]

[tex]T = 0.6[/tex]

[tex]T=I \alpha[/tex]

[tex]T = 12RPM^2[/tex] Units?

im guessing this is wrong because I never had to use the mass anywhere

Can anyone help?

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- Thread starter suspenc3
- Start date

- #1

suspenc3

- 402

- 0

r=0.2m

I=0.05kg(m^2)

m=2kg

P=3.0N

[tex]T = rFsin \theta[/tex]

[tex]T = 0.6[/tex]

[tex]T=I \alpha[/tex]

[tex]T = 12RPM^2[/tex] Units?

im guessing this is wrong because I never had to use the mass anywhere

Can anyone help?

- #2

suspenc3

- 402

- 0

Any help would be appreciated

- #3

Fermat

Homework Helper

- 872

- 1

The cord that is wrapped around the wheel. It comes off the top or bottom of the wheel ?

Is the cord at an angle when it comes off the wheel, or is is horizontal ?

Is this cord then horizontally attached to the 2kbg block ?

Is the 2 kg block resting on a frictionless surface ?

- #4

suspenc3

- 402

- 0

its horizontal

yes its horizontally attached

yes its on a frictionless surface

yes its horizontally attached

yes its on a frictionless surface

- #5

Fermat

Homework Helper

- 872

- 1

You have a force P applied to the 2 kg block.

This force accelerates both the 2kg block and the Wheel.

Divide up this force into two components, F1 and F2. Obviously F1 + F2 = P

Let F1 be the accelerating force on the 2kg block.

Let F2 provide the accelerating torque on the wheel.

Since they are both attached, then the linear acceleration of the circumference of the wheel matches the linear acceleration of the 2 kg block.

Can you work things out from this ?

- #6

suspenc3

- 402

- 0

hmm..im still not surbe I understand

Im trying ot find F2?

P is known

how would i calculate F1?

Im trying ot find F2?

P is known

how would i calculate F1?

- #7

Fermat

Homework Helper

- 872

- 1

You create expressions involving F1 and F2 and then add the expressions together to equal P. F1 +F2 = P.

F1 is the accelerating force on the 2kg block, ergo

F1 = ma (m = 2kg)

F2 provides the torque on the wheel, ergo

F2*r = I*alpha

ergo²,

F1 + F2 = P

ma + I*alpha/r = P

The only unknowns now are a and alpha, the linear and angular accelerations.

You have to find a relatoinshipo between them. Remember my comment in my earlier post.

- #8

suspenc3

- 402

- 0

so a=alpha(r)

- #9

Fermat

Homework Helper

- 872

- 1

Yep, that's it

The rest should fall out now.

The rest should fall out now.

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