# Force on roll of paper - length of paper that unrolls

1. Oct 28, 2004

### physicsss

The radius of the roll of paper is 7.6 cm and its moment of inertia is I = 2.9 10^-3 kg · m2. A force of 3.2 N is exerted on the end of the roll for 1.3 s, but the paper does not tear so it begins to unroll. A constant friction torque of 0.11 m · N is exerted on the roll which gradually brings it to a stop. Assume that the paper's thickness is negligible.

(a) Calculate the length of paper that unrolls during the time that the force is applied (1.3 s).

(b) Calculate the length of paper that unrolls from the time the force ends to the time when the roll has stopped moving.

2. Oct 28, 2004

### Sirus

Have you tried it?

Consider these formulas:
$$\sum{\tau}=I\alpha$$
$$\tau=Fl$$
where $\alpha$ is angular acceleration and $l$ is length of the lever arm.