1.9/1.10-Work and Power Practice Assessment

What is the SI unit for power?

• Watt

• Joule

• Newton

• Kilogram

Answer explanation

The SI unit for power is the Watt, which measures the rate of energy transfer. Joule measures energy, Newton measures force, and Kilogram measures mass, making Watt the correct choice for power.

What is the SI unit for work?

• Watt

• Joule

• Newton

• Kilogram

Answer explanation

The SI unit for work is the Joule, which is defined as the amount of energy transferred when a force of one Newton is applied over a distance of one meter. Watt measures power, not work.

Tags

NGSS.HS-PS2-1

How is work calculated?

• Hours per day spent at a job

• Force times distance

• Power times distance

• Force times time

• Power divided by distance

Answer explanation

Work is calculated as force times distance (W = F × d). This formula shows that work is done when a force moves an object over a distance, making 'Force times distance' the correct choice.

How is power calculated

• Force times time

• Work divided by time

• Work times time

• Force divided by time

• Work divided by force

Answer explanation

Power is calculated as work done over time. This means that the correct choice is 'Work divided by time', which reflects how quickly work is performed.

What information do you need to find power? Select all that apply

• Work

• Time

• Energy

• Type of object

Answer explanation

To find power, you need to know the work done and the time taken. Power is calculated as work divided by time (Power = Work/Time). Energy is related but not directly needed for this calculation.

What must happen for work to be done? Select all that apply.

• No friction can be present

• A force must be exerted on an object

• The object must move in any direction

• The object must move in the direction of the force

Answer explanation

For work to be done, a force must be exerted on an object, and the object must move in the direction of that force. Movement in any direction without this alignment does not constitute work.

Using a force of 50 N you push a shopping cart 10 m. How much work did you do?

• 5 J

• 0.2 J

• 50 J

• 500 J

Answer explanation

Work is calculated using the formula: Work = Force x Distance. Here, Work = 50 N x 10 m = 500 J. Therefore, the correct answer is 500 J.

A teacher pushed his car with a force of 9,000 Newtons but was unable to move it. How much work did he do?

• 0 J

• 9,000 J

• 918 J

• 9.8 J

Answer explanation

The work done is calculated as force times distance. Since the car did not move, the distance is 0. Therefore, the work done is 0 J, making the correct answer 0 J.

Tags

NGSS.MS-PS2-2

Two students with the same weight climb a flight of stairs. Student A walks slowly up the stairs. Student B runs up the stairs. Which student did more work?

• Student A

• Student B

• They did the same amount of work

Answer explanation

Work is defined as force times distance. Both students climb the same height and have the same weight, so they exert the same force over the same distance. Therefore, they did the same amount of work.

Tags

NGSS.MS-PS3-1

NGSS.MS-PS3-5

Two students with the same weight climb a flight of stairs. Student A walks slowly up the stairs. Student B runs up the stairs. Which student used more power?

• Student A

• Student B

• They did the same amount of work

Answer explanation

Student B used more power because power is the rate of doing work. Running up the stairs requires more energy in a shorter time compared to walking slowly, resulting in higher power output.

Tags

NGSS.MS-PS3-1

NGSS.MS-PS3-5