Q: A 1200 kg elevator slows from 4 m/s to rest in 2 seconds while moving upward. What is the tension $$T in $$the cable during this time? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

$$T = 1200 \times (9.8 - 2) = 9,360\ \mathrm{N}$$

Q: A person stands on a scale in an elevator that is accelerating downward at $$2\ \mathrm{m/s^2$}. If $$the person's mass is 70 kg, what does the scale read?

$$70 \times (9.8 - 2) = 546\ \mathrm{N}$$

Question 1

An elevator is moving upward but slowing down as it approaches a floor. Which of the following best describes the direction of the net force acting on the elevator during this stage?

Accepted Answer

The net force is downward because the elevator is decelerating while moving upward.

Question 2

A 1200 kg elevator slows from 4 m/s to rest in 2 seconds while moving upward. What is the tension $$T in $$the cable during this time? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$T = 1200 	imes (9.8 - 2) = 9,360\ \mathrm{N}$$

Question 3

Which free-body diagram correctly represents the forces acting on an elevator moving upward while slowing down?

Accepted Answer

The diagram where the downward arrow (weight) is longer than the upward arrow (tension).

Question 4

A person stands on a scale in an elevator. When does the scale reading (apparent weight) become greater than the actual weight?

Accepted Answer

When the elevator is accelerating upward.

Question 5

What does a bathroom scale actually measure when you stand on it in an elevator?

Accepted Answer

The normal force exerted by the scale on you.

Question 6

If a 5.0 kg block is placed on a scale and the scale reads 70 N, what can you conclude about the block's motion?

Accepted Answer

The block is accelerating upward.

Question 7

Which of the following best describes 'apparent weight'?

Accepted Answer

The support force you feel from the surface you are on.

Question 8

A person stands on a scale in an elevator that is accelerating downward at $$2\ \mathrm{m/s^2$}. If $$the person's mass is 70 kg, what does the scale read?

Accepted Answer

$$70 	imes (9.8 - 2) = 546\ \mathrm{N}$$

Question 9

During which stage of an elevator ride will a passenger feel 'weightless'?

Accepted Answer

When the elevator is in free fall (cable snaps).

Question 10

A velocity vs. time graph for an elevator shows a straight line with negative slope. What does the area under the curve represent?

Accepted Answer

The displacement of the elevator.

Question 11

If the net force on an object is zero, what can you say about its motion?

Accepted Answer

It could be moving at constant velocity.

Question 12

A 5.0 kg block is on a scale in an elevator. The scale reads 0 N. What is happening to the block?

Accepted Answer

The block is in free fall.

Question 13

Which kinematic equation would you use to find the distance traveled by an elevator that starts at 4 m/s and comes to rest in 2 seconds with constant acceleration?

Accepted Answer

$$x_f = x_i + v_{x,i} \Delta t + \frac{1}{2} a_x (\Delta t)^2$

Question 14

If a scale is on a tilted floor, what will it measure?

Accepted Answer

The component of the normal force perpendicular to the scale's surface.

Question 15

A person jumps onto a scale quickly. What will the scale reading show at the instant of landing?

Accepted Answer

More than the person's weight.

Question 16

Which of the following is true about the mass, weight, and apparent weight of a person riding an elevator?

Accepted Answer

Mass stays the same, weight stays the same, but apparent weight can change.

Question 17

A 5.0 kg block is held at rest on a scale. What is the normal force exerted by the scale?

Accepted Answer

$$49\ \mathrm{N}$$

Question 18

Which of the following best explains why you feel heavier than normal when an elevator accelerates upward?

Accepted Answer

The normal force (apparent weight) increases due to upward acceleration.

Question 19

A person stands on a scale in an elevator that is moving downward at constant speed. What does the scale read?

Accepted Answer

Equal to the person's weight.

EXAM #3: DAY 12 Vertical Dynamics and Apparent Weight in Elevator Motion

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