{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

7 Work and Energy ay-1

# 7 Work and Energy ay-1 - Chapter 7 Work and Energy 1 7-1...

This preview shows pages 1–9. Sign up to view the full content.

1 Chapter 7 Work and Energy

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 7-1 Work Done by a Constant Force Work is the product of the magnitude of the displacement times the component of force parallel to the displacement. In the SI system, work is measured in joules. Work is a scalar quantity. [W] = (N)(m) = joules
3 Work Done by a Constant Force W = F d W = Fd cos θ

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
4 A B = AB cos θ Therefore we can write the work done by a constant force as the dot product of the force and displacement: W = F d = Fd cos θ Scalar Product of Two Vectors
5 Important • Must specify (as with force) if work is done on the object or by the object. • Must specify if work is done by one particular force or by the net force. • If net force, you get net (or total) work. No net work done by the pulling force!

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Example A car is taking a turn. How much work does friction on the car? F friction Δ d Friction is directed radially The displacement is tangent to the path There is no force parallel to the displacement! W = F friction Δ d = 0 Example What is the work that the Earth does on the Moon? Force acting on the Moon: Gravitational Force W = 0 v F G perpendicular to displacement
6 Example 7-1 Work done on a create. A 50-kg create is pulled 40 m along a horizontal floor by a constant force exerted by a person, F P = 100 N, which acts at a 37 o angle as shown in the figure. The floor is rough and exerts a friction force F fr = 50 N. Determine the work done by each force acting on the create, and the net work done on the create.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
7 Work on a carried backpack. ( a ) Determine the work a hiker must do on a 15.0-kg backpack to carry it up a hill of height h = 10.0 m, as shown in the figure. ( b ) Determine the work done by gravity on the backpack. ( c ) Determine the net work done on the backpack. For simplicity, assume the motion is smooth and at a constant velocity (i.e., a =0).
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 25

7 Work and Energy ay-1 - Chapter 7 Work and Energy 1 7-1...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online