- #1

Jamie_Pi

- 18

- 0

## Homework Statement

The two blocks,

*m*1 = 3.3 kg and

*m*2 = 4.8, in the figure below are connected by a massless rope that passes over a pulley. The pulley is 12 cm in diameter and has a mass of 2.0 kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.64 N · m. If the blocks are released from rest, how long does it take the 4.8 kg block to reach the floor from a height of

*h*= 1.0 m? (Note: If your random numbers do not create movement between the masses enter 0 for your answer.)

## Homework Equations

Torque=Force*Radius

Torque=moment of inertia*angular acceleration

angular acceleration = linear acceleration/radius

s=1/2*linear acceleration*time^2

## The Attempt at a Solution

I tried to calculate the torque on the pulley and convert that to linear acceleration, and find the time from that.

Torque total= m*g*r-friction

Torque total=4.8*9.8*0.06-4.8*9.8*0.06-0.64

Torque total=0.4004

moment of inertia=1/2*mass*radius^2

moment of inertia=0.0036

0.4004=0.0036*angular acceleration

angular acceleration=111.22

111.22=linear acceleration/0.06

linear acceleration=6.6733

s=3.337*t^2

1=3.337*t^2

t=sqrt(1/3.337)

t=0.5441

I did something wrong, and I'm not sure what. I'm not very good with rotation and torque, though, so I don't know where my mistake could be. The real answer is 2.12 seconds.