Power And Work Quiz

2.

A constant force of 10 N causes a box to move at a constant speed of 2 m/s. How much power is done in 10 seconds?

200W
20W
2W
2000W

Correct Answer

A. 20W

Explanation

The power is calculated by multiplying the force applied to an object by the object's velocity. In this case, the constant force is 10 N and the constant speed is 2 m/s. Thus, the power is 10 N x 2 m/s = 20 W.

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3.

Power is defined as:

Work per unit length (W/d)
Work times time (W∙t)
Force per unit length (F/d)
Work per unit time (W/t)

Correct Answer

A. Work per unit time (W/t)

Explanation

The correct answer is "Work per unit time (W/t)". Power is defined as the rate at which work is done or the amount of work done per unit time. It represents how quickly energy is transferred or converted. Therefore, power is calculated by dividing the amount of work done by the time taken to do that work.

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4.

Liz throws a softball with a force of 63 N a distance of 25 m. Jamie throws the softball with the twice amount of force, but the ball only goes 17 m. Which girl does less work?

Jamie
Liz
Both are the same
Option 4

Correct Answer

A. Liz

Explanation

Liz does less work because work is calculated by multiplying force and distance. Since Liz throws the softball with a force of 63 N and a distance of 25 m, her work is 63 N * 25 m = 1575 Nm. On the other hand, Jamie throws the softball with twice the force (126 N) but the ball only goes 17 m. Therefore, Jamie's work is 126 N * 17 m = 2142 Nm, which is greater than Liz's work. Therefore, Liz does less work.

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5.

A student is running up 3 flights of stairs. He runs up the first flight quickly but the last two he tires so goes a little slower. When does he exert more power and why?

The last flight because he is tired and trying more
The first flight because he takes less time
The second flight because he takes more time
The power is the same for all three flights of stairs

Correct Answer

A. The first flight because he takes less time

Explanation

The student exerts more power on the first flight because he takes less time to complete it. Power is defined as the rate at which work is done or energy is transferred. Since the student is running up the stairs quickly on the first flight, he is doing work at a faster rate, resulting in more power exerted.

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6.

In a period of 10 seconds, an elevator lifts a weight of 1000 N a distance of 10 m at constant velocity. What is the average power of the elevator over this time?

1000W
10000W
10W
100W

Correct Answer

A. 1000W

Explanation

The average power of the elevator can be calculated by dividing the work done by the elevator by the time taken. In this case, the work done is equal to the force applied (1000N) multiplied by the distance covered (10m), which is 10000J. The time taken is 10 seconds. Therefore, the average power is 10000J/10s = 1000W.

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7.

How much energy is needed to run a 75-watt light bulb for 6 seconds?

12.5J
100J
450J
5J

Correct Answer

A. 450J

Explanation

The energy needed to run a light bulb can be calculated using the formula E = P * t, where E is the energy, P is the power, and t is the time. In this case, the power of the light bulb is given as 75 watts, and the time is given as 6 seconds. Plugging these values into the formula, we get E = 75 watts * 6 seconds = 450 joules. Therefore, the correct answer is 450J.

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8.

How is work related to acceleration?

W = m∙a
W = m∙a∙t
W = m∙a∙d
W = m∙a/d

Correct Answer

A. W = m∙a∙d

Explanation

The equation W = m∙a∙d represents the work done on an object. In this equation, W represents work, m represents mass, a represents acceleration, and d represents distance. The equation shows that work is directly proportional to both mass and acceleration, as well as the distance over which the force is applied. This means that as either mass or acceleration increases, the amount of work done also increases. Similarly, if the distance over which the force is applied increases, the amount of work done also increases. Therefore, the equation W = m∙a∙d accurately represents the relationship between work and acceleration.

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9.

A machine using a power of 1000W requires a force of 100 N to raise a mass in 10 s. The height the mass is raised in this time is

10000m
1000m
10m
100m

Correct Answer

A. 100m

Explanation

The work done by a machine can be calculated by multiplying the force applied by the distance over which the force is applied. In this case, the force required is 100 N and the time taken is 10 seconds. Since power is equal to work divided by time, we can calculate the work done by the machine as 1000W x 10s = 10000 J. Given that the force required is 100 N, we can use the formula work = force x distance to find the distance. Rearranging the formula, we get distance = work / force = 10000 J / 100 N = 100 m. Therefore, the height the mass is raised in this time is 100 meters.

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10.

An escalator is used to move 20 passengers every minute from the first floor of a department store to the second. The second floor is located 5.20 meters above the first floor. The average passenger's mass is 54.9 kg. Determine the POWER requirement of the escalator in order to move this number of passengers in one minute.

47 Watts
55954 Joules
2797 Joules
951.6 Watts

Correct Answer

A. 951.6 Watts

Explanation

The power requirement of the escalator can be calculated using the formula: Power = Work / Time. The work done by the escalator is equal to the force applied (mass of passengers multiplied by acceleration due to gravity) multiplied by the distance traveled (height of the second floor). The time taken is given as one minute. Plugging in the values, we can calculate the power requirement to be 951.6 Watts.

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Power And Work Quiz

The units of power are:

Quiz Preview

A constant force of 10 N causes a box to move at a constant speed of 2 m/s. How much power is done in 10 seconds?

Power is defined as:

Liz throws a softball with a force of 63 N a distance of 25 m. Jamie throws the softball with the twice amount of force, but the ball only goes 17 m. Which girl does less work?

A student is running up 3 flights of stairs. He runs up the first flight quickly but the last two he tires so goes a little slower. When does he exert more power and why?

In a period of 10 seconds, an elevator lifts a weight of 1000 N a distance of 10 m at constant velocity. What is the average power of the elevator over this time?

How much energy is needed to run a 75-watt light bulb for 6 seconds?

How is work related to acceleration?

A machine using a power of 1000W requires a force of 100 N to raise a mass in 10 s. The height the mass is raised in this time is