Question

You throw a Frisbee of mass m and radius r so that it is spinning about a horizontal axis perpendicular to the plane of the Frisbee. Ignoring air resistance, the torque exerted about its center of mass by gravity is: __________

a. 0.
b. mgr
c. 2mgr
d. a function of the angular velocity.
e. small at first, then increasing as the Frisbee loses the torque given it by your hand.

Answer 1

the correct answer is a

Step-by-step explanation:

The torque is

τ = F x r

where the bold letters indicate vectors, in this case the vector of the center of mass is perpendicular to the weight of the body

τ = mg r

in body weight it is applied at the point of the center of mass, therefore as the distance of the force from the axis of rotation (center of amas) is zero, the die is zero

the correct answer is a