Rotational Equilibrium

 

Torque can be described as

• the ratio of mass to angular acceleration

• None of the other answer

• the ratio of moment of inertial to angular acceleration

• how effectively a force causes a rotation

 

How is torque calculated using the moment arm?

• τ = Fr

• τ = F/r

• τ = r/F

• τ = F + r

The lever arm is the ________ distance from the axis of rotation to the point where the force is exerted.

• perpendicular

• angular

• displaced

• none of these

The moment of a 50 N force 20 cm away from the pivot point will be.

• 10 Nm

• 500 Nm

• 20 Nm

• 15 Nm

Suppose a doorknob is placed at the center of a door. Compared with a door whose knob is located at the edge, what amount of force must be applied to this door to produce the torque needed to open it?

• Four times as much

• 1/4 as much

• 1/2 as much

• Twice as much

A thin, 1 m-long rod has a 200 g object attached to the left end and a 300 g object attached to the right end. If the pivot point is in the middle of the rod, the object

Note: with negligible mass for the rod

• will rotate clockwise

• will be in static rotational equilibrium

• is balanced

• will rotate counter clockwise

The easiest way to open a heavy door  is by applying the force

• At the edge of the door far from the hinges

• At the top of the door

• Near the hinges

• In the middle of the door

If the kid on the left weights 490 N, 0.5m away from the pivot point, then the second kid must have _____ in order to keep it in static equilibrium

• 490 N, 0.5m away from the pivot point to the right

• 340 N, 0.1 m away from the pivot point to the right

• 220 N, 0.2 m away from the pivot point to the left

Conditions for equilibrium are:

1st condition: net force = 0

2nd condition: net torque = 0

Moving with constant velocity or stationary/rest

• False

• True

A little girl whose mass is 20 kg is sitting on a swing attached by two ropes, as shown. The mass of the rope and swing is negligible. What is the tension in the ropes?

• 19,600 N

• 196 N

• 20 N

• 2.04 N