Assignment Redo: Calculating Work, Power, and Efficency

A motor does 200 J of work in 10 seconds. What is the power output of the motor?

The formula for power is Power (W) = Work (J) / Time (s).

• 10 W

• 20 W

• 30 W

• 40 W

The formula for power is Power (W) = Work (J) / Time (s).

A light bulb uses 60 J of energy in 2 seconds. What is the power of the light bulb?

• 15 W

• 20 W

• 25 W

• 30 W

A crane lifts a 500 J load in 25 seconds. What is the power of the crane?

The formula for power is Power (W) = Work (J) / Time (s).

• 25 W

• 20 W

• 15 W

• 10 W

The formula for power is Power (W) = Work (J) / Time (s).

A student does 150 J of work in 5 seconds. What is the power output of the student?

• 25 W

• 35 W

• 30 W

• 20 W

A machine performs 300 J of work in 15 seconds. What is the power of the machine?

The formula for power is Power (W) = Work (J) / Time (s).

• 25 W

• 15 W

• 30 W

• 20 W

The work input of a screwdriver is 100 J. The work output of the screwdriver is 80 J.

What is the efficiency of the screwdriver?

The formulas for Efficiency are (Work Output / Work Input) x 100 and

(Mechanical Advantage / Speed Ratio) x 100.

• 70%

• 75%

• 80%

• 85%

Tags

NGSS.MS-PS3-5

The formulas for Efficiency are (Work Output / Work Input) x 100 and

(Mechanical Advantage / Speed Ratio) x 100.

A cyclist sprinter does 1,000 J of work in a race.

While their bike does 600 J of work during the race. What is the efficiency of the bike?

• 60%

• 65%

• 50%

• 55%

An inclined plane provides 600 J of work as compared to the 400 J of work done by the user.

What is the efficiency of the simple machine? Is this efficiency possible?

The formulas for Efficiency are (Work Output / Work Input) x 100 and

(Mechanical Advantage / Speed Ratio) x 100.

• 100%

• 125%

• 150% - An efficiency greater than 100% is possible because it means the machine is producing more work than the energy put into it, which suggests that the machine is creating energy. In an ideal world, machines can be perfectly efficient, and no energy is lost to friction, heat, or other inefficiencies, so the efficiency of a machine can exceed 100%.

• 150% - An efficiency greater than 100% is not possible because it implies that the machine is producing more work than the energy put into it, which violates the law of conservation of energy. In real-world scenarios, some energy is always lost due to factors like friction, heat, and other inefficiencies, so the efficiency of a machine is always less than or equal to 100%.

An inclined plane provides 600 J of work as compared to the 400 J of work done by the user.

What is the efficiency of the simple machine? Is this efficiency possible?

The formulas for Efficiency are (Work Output / Work Input) x 100 and

(Mechanical Advantage / Speed Ratio) x 100.

• 100%

• 125%

• 150% - An efficiency greater than 100% is possible because it means the machine is producing more work than the energy put into it, which suggests that the machine is creating energy. In an ideal world, machines can be perfectly efficient, and no energy is lost to friction, heat, or other inefficiencies, so the efficiency of a machine can exceed 100%.

• 150% - An efficiency greater than 100% is not possible because it implies that the machine is producing more work than the energy put into it, which violates the law of conservation of energy. In real-world scenarios, some energy is always lost due to factors like friction, heat, and other inefficiencies, so the efficiency of a machine is always less than or equal to 100%.

Tags

NGSS.MS-PS3-4

The formulas for Efficiency are (Work Output / Work Input) x 100 and

(Mechanical Advantage / Speed Ratio) x 100.

It takes 60 J of work to move a box with a 70% efficient pulley.

How much work must the user do to move the box?

• 85.71 J

• 95.71 J

• 80 J

• 90 J