Big Picture MS-PS3-1. Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object. PS3.A: Definitions of Energy Motion energy is properly called kinetic energy; it is proportional to the mass of the moving object and grows with the square of its speed. (MS-PS3-1)
Do Now First, in your science journal, define what specific kind of work is being done in each activity below. Then, select the activities that require the least amount of work. carrying heavy books home reading a 300-page novel skiing for 1 hour lifting a 45 kg mass holding a steel beam in place for 3 hours jacking up a car
Objectives: Determine when work is being done on an object. Calculate the amount of work done on an object. Explain the difference between work and power. Learning Target Today I will: Learn when work is being done on an object. So that I can: Calculate the amount of work on an object. I will know I got it if: I can explain work and calculate sample problems involving work. Agenda Today we will: Learn about work and power from a teacher presentation. Complete a do now. Begin group activity.
Vocabulary work power joule watt
What Is Work? Work is the transfer of energy to an object by using a force that causes the object to move in the direction of the force. Transfer of Energy One way you can tell that work is being done is that energy is transferred.
What Is Work?, continued Difference Between Force and Work Applying a force doesn’t always result in work being done. Force and Motion in the Same Direction For work to be done on an object, the object must move in the same direction as the force.
How Much Work? Same Work, Different Force Work depends on distance as well as force.
How Much Work?, continued Calculating Work The amount of work (W) done in moving an object can be calculated by multiplying the force (F) applied to the object by the distance (d) through which the force is applied: The unit used to express work is the newton-meter (N m), which is more simply called the joule. W F d
Power: How Fast Work Is Done Calculating Power Power is the rate at which energy is transferred. To calculate power (P), you divide the amount of work done (W) by the time (t) it takes to do that work: The unit used to express power is joules per second (J/s), also called the watt. One watt (W) is equal to 1 J/s. P W t
Power: How Fast Work Is Done, continued Increasing Power It may take you longer to sand a wooden shelf by hand than by using an electric sander, but the amount of energy needed is the same either way. Only the power output is lower when you sand the shelf by hand.
Exit Ticket What is work and how is related to energy?