Forces, Torque, and Motion Flashcards

An elevator safety gear grips the guide rails to stop the car. The stopping force is an example of:

Answer: Friction force

Safety gear clamps the rail and uses friction to decelerate and stop the car.

If a motor's output torque doubles while its rotational speed stays the same, what happens to its output power?

Answer: Power doubles

Power = Torque × angular velocity; doubling torque at constant speed doubles power.

A 1,000 kg elevator car is at rest. What is the tension in the supporting rope? (g = 9.8 m/s²)

Answer: 9,800 N

At rest (no acceleration), tension equals weight = 1,000 × 9.8 = 9,800 N.

Which condition must be true for an object to be in rotational equilibrium?

Answer: Both net force and net torque = 0

Complete mechanical equilibrium requires both zero net force (translational) and zero net torque (rotational).

An elevator travels from floor 1 to floor 10, accelerates for 2 s, travels at constant speed for 8 s, then decelerates for 2 s. During which phase is the rope tension greatest?

Answer: Acceleration phase

During upward acceleration, the rope must support the car's weight plus provide the net upward force, making tension greatest.

A hydraulic elevator piston has an area of 0.05 m² and supports a load requiring 50,000 N. What fluid pressure is needed?

Answer: 1,000,000 Pa

Pressure = Force / Area = 50,000 / 0.05 = 1,000,000 Pa (1 MPa).

When a rotating drum's radius is doubled while keeping torque constant, what happens to the rope tension it can produce?

Answer: Tension is halved

Tension = Torque / radius; doubling radius with constant torque halves the tension.