CW 107

Two masses of mass 10.0 and 6.0 kg are hung from massless strings at the end of a light rod. The rod is virtually weightless. A pivot (fulcrum) is placed off center and the system is free to rotate. If the 6.0 kg mass is 4.0 m away from the pivot, how far away is the 10.0 kg mass if the system is not rotating?

• 0.42 m

• 2.4 m

• 4.8 m

• 4.2 m

Two masses of mass 10.0 and 6.0 kg are hung from massless strings at the end of a light rod. The rod is virtually weightless. A pivot (fulcrum) is placed off center and the system is free to rotate. If the string supporting the 10 kg mass is cut, find the net torque of the system.

• 24 Nm

• 60 Nm

• 240 Nm

• 480 Nm

1. Which of the following must be true for the system of two concentric massless pulleys and two masses shown in the picture for the system to be at equilibrium?

• m₁ = m₂

• m₁R₁ = m₂R₂

• m₁R₂ = m₂R₁

• m₁R₁² = m₂R₂²

Tags

NGSS.HS-PS2-1

A wrench is used to tighten a nut. A 15N perpendicular force is applied 50cm away from the axis of rotation, and moves a distance of 10 cm as it turns. What is the torque applied to the wrench?

• 7.5 Nm
• 1.5 Nm
• 750 Nm
• 150 Nm

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

• Near the hinges
• In the middle of the door
• At the edge of the door far from the hinges
• At the top of the door

In the diagram above, two masses, one with mass m, the other with mass M = 2m are resting on a uniform plank of length L that pivots at its midpoint. If the mass m is at the far end of the plank, how far away from the pivot should the mass M be to balance the plank in a horizontal position shown?

• L/2
• L/3
• L/4
• L/6

A large disc with varying diameters is free to rotate about its axis located in the geometric center of the disc. According to the picture above, what will happen when the masses are released and the disc is free to rotate?

• The disc will spin clockwise, because the heavier mass exerts a large force on the disc, thus creating a large torque in the clockwise direction.

• The disc will spin counterclockwise, because the lighter mass applies a force to a longer lever-arm (r), thus creating more torque in the counterclockwise direction.

• The clock will not spin clockwise or counterclockwise because the torque produced by each hanging mass is equal, which puts the system in equilibrium and there will be no angular acceleration.

• It's impossible to tell which direction this wheel will rotate based on the diagram alone.

Tags

NGSS.HS-PS2-1

If the torque required to loosen a nut on the wheel of a car has a magnitude of 60.0 N• m, what minimum perpendicular force must be exerted by a mechanic at the end of a 45.0 cm wrench to loosen the nut?

• 0.666 Nm
•  133.3 N
• 66.7 N
• 13.3 Nm

A state of equilibrium is also seen below. Each of the cars weighs the same  9800 N. Despite the fact that there is only one car on the left-hand side that is 9 m from the fulcrum, the torques balance because, the car on the left-hand side, is ____meters from the fulcrum, compared to the cars on the right-hand side.

• 4.5 m
• 3 m
• 1 m
• 2 m

Find the magnitude of the torque produced by a 5.0 N force applied to a door at a perpendicular distance of 65 cm from the hinge.

• 75 Nm
• 3.25 Nm
• 6.3 Nm
• 8.75 Nm