EIAT - Elevator Industry Aptitude Forces, Torque, and Motion Questions and Answers

Question 1

An elevator motor needs to generate torque to lift the car. If the radius of the motor's drive sheave is 0.5 meters and the force required to lift the elevator car and its contents is 8,000 Newtons, what is the minimum torque the motor must produce to begin lifting the car, ignoring friction and other losses?

Accepted Answer

4,000 N·m

Answer

Torque is calculated as the product of the force and the radius (lever arm) at which the force is applied (Torque = Force × Radius). In this scenario, the force is 8,000 N and the radius of the sheave is 0.5 m. Therefore, the torque required is 8,000 N × 0.5 m = 4,000 N·m.

Question 2

A technician is inside an elevator that is accelerating upwards at a constant rate. How does the normal force exerted by the elevator floor on the technician compare to the technician's actual weight (the force of gravity)?

Accepted Answer

The normal force is greater than their weight.

Answer

According to Newton's Second Law (F=ma), a net force is required for acceleration. For the technician to accelerate upwards, the upward force (normal force from the floor) must be greater than the downward force (gravity/weight). This net upward force causes the upward acceleration, making the person feel heavier.

Question 3

A technician needs to slide a heavy, stationary piece of equipment across a machine room floor. Which of the following statements about the forces involved is most accurate?

Accepted Answer

The force required to start the equipment moving is greater than the force required to keep it sliding.

Answer

The force of static friction, which prevents an object from moving, is generally greater than the force of kinetic (or sliding) friction, which opposes motion once the object is already moving. Therefore, more force is needed to overcome static friction and start the movement than to overcome kinetic friction and maintain the movement.

Question 4

In an elevator system, the motor provides the most torque during which phase of operation?

Accepted Answer

During initial acceleration from a stop.

Answer

The greatest torque is required to overcome inertia—the resistance of the heavy elevator car to changes in its state of motion. This occurs during the initial acceleration from a standstill. Once the car is moving at a constant speed, the torque needed is less because it only has to overcome friction and the net weight difference, not inertia.

Question 5

An elevator car with a mass of 1,200 kg is perfectly balanced by a counterweight of 1,200 kg. Ignoring friction, what is the net force required from the hoisting machine to make the car travel upwards at a constant velocity?

Accepted Answer

0 N

Answer

According to Newton's First Law, an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Since the elevator is moving at a constant velocity (zero acceleration) and the car is perfectly balanced by the counterweight, no net force is required to maintain this motion, assuming no friction. The motor only needs to overcome any system friction.

EIAT - Elevator Industry Aptitude Test Practice Test

EIAT - Elevator Industry Aptitude Test Practice Test

EIAT - Elevator Industry Aptitude Forces, Torque, and Motion Questions and Answers