University:
High School
Course:
High School Physics
Academic year:

2022
Views:

359

Pages:

2
Author:

StellarStrategist

Name: __________________________________________________________________________________ Date: ________________________ Period: _________ Calculating Work and Power Directions: Identify givens, unknown, equation and then solve for the unknown variable for the following problems that require calculations. 1. In science, “work” is defined with an __________________. Work is the amount of __________________ applied to an object (in the __________________ direction as the motion) over a _____________________. By measuring how much force you have used to move something over a certain distance, you can calculate how much work you have accomplished. Work can also cause a change in __________________. Power is the rate of doing __________________. You do work if you lift a heavy box up a flight of stairs. You do the same amount of work whether you lift the box slowly or quickly. But your power is greater if you do the work in a __________________ amount of time. Power can also be used to describe the rate at which energy is ___________________ from one form into another. 2. Complete the following data table: Force (N) Distance (m) Time (sec) 100 2 5 100 1 10 100 4 10 100 9 25 500 20 20 1000 30 10 Power (W) 60 20 3 3. Work (J) 60 75 5 A 200 N box is lifted to a height of 4 m. a. How much work is done in lifting the box to this height? b. The box is then accidentally dropped. What is the speed of the box right before it hits the ground? 4. You did 150 J of work lifting a 12 kg backpack. How high did you lift the backpack? 5. An alkaline AA battery stores approximately 12,000 joules of energy. A small flashlight uses two AA batteries and will produce light for 2.0 hours. What is the power of the flashlight bulb? Assume all of the energy in the batteries is used. 6. 7. Oliver weighs 600 newtons. He climbs a flight of stairs that is 3.0 meters tall in 4.0 seconds. a. How much work did he do? b. What was Oliver’s power during this time? c. Sally completed the same task in 6 seconds. Who did more work? How do you know? An elevator weighing 6,000 N moves up a distance of 10.0 meters in 30.0 seconds. a. How much work did the elevator’s motor do? b. 8. 9. What was the power of the elevator’s motor? The power of a typical adult’s body over the course of a day is 100 watts. This means that 100 joules of energy from food are needed each second. a. An average apple contains 500,000 joules of energy. For how many seconds would an apple power a person? b. How many joules are needed each day? c. How many apples would a person need to eat to get enough energy for one day? The block shown to the right has a mass of 50 kg. a. How much potential energy, relative to the ground would it have at the top of the incline? b. How much work was needed to push the block up the ramp? c. What force was required to push the block up the ramp? 10. A 40 kg crate sits on a frozen lake. a. If you pushed on it with a force of 5 N for a distance of 4m, how much kinetic energy would it have? b. How fast would it be going?