1 / 7

Aim: How can we describe power?

Aim: How can we describe power?. Answer Key HW #7. Do Now: A 50 kg box is lifted 10 m in 30 s. How much was was done? W = Fx W = F g h W = mgh W = (50 kg)(10 m/s 2 )(10 m) W = 5,000 J. **No Calculator** 1 min. Power. The rate of doing work Rate means divide by time Scalar quantity.

saad
Télécharger la présentation

Aim: How can we describe power?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Aim: How can we describe power? Answer Key HW #7 Do Now: A 50 kg box is lifted 10 m in 30 s. How much was was done? W = Fx W = Fgh W = mgh W = (50 kg)(10 m/s2)(10 m) W = 5,000 J **No Calculator** 1 min

  2. Power • The rate of doing work • Rate means divide by time • Scalar quantity James Watt 1736-1819 Units:

  3. 1. A person pushes a box across a horizontal surface at a constant speed of 0.5 meter per second. The box has a mass of 40 kilograms, and the coefficient of sliding friction is 0.25. The power supplied to the box by the person is • 0.2 W • 5 W • 50 W • 100 W • 200 W **No Calculator** 1 min 15 sec

  4. 2. A weight lifter lifts a mass m at constant speed to a height h in time t. What is the average power output of the weight lifter? • mg • mh • mgh • mght • mgh /t **No Calculator** 1 min 15 sec

  5. 3. A student weighing 700 N climbs at constant speed to the top of an 8 m vertical rope in 10 s. The average power expended by the student to overcome gravity is most nearly • 1.1 W • 87.5 W • 560 W • 875 W • 5,600 W **No Calculator** 1 min 15 sec

  6. 4. Units of power include which of the following? • I. Watt • II. Joule per second • III. Kilowatt‑hour • I only • III only • (C) I and II only • (D) II and III only • (E) I, II, and III I – Watt is the unit of power II – This is W/t (or power) III – This is Pt which equals W **No Calculator** 1 min

  7. 5. A child pushes horizontally on a box of mass m which moves with constant speed v across a horizontal floor. The coefficient of friction between the box and the floor is . At what rate does the child do work on the box? • mgv • (B) mgv • (C) mg/v • (D) mg/v • (E) mv2 **No Calculator** 1 min 15 sec

More Related