1 / 10

Net Work

Net Work. Net work (W net ) is the sum of the work done on an object by all forces acting upon the object. The Work-Energy Theorem. Consider a force applied to an object ( Σ F ≠ 0). Newton’s second law tells us that this net force will produce an acceleration.

niabi
Download Presentation

Net Work

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. Net Work Net work (Wnet) is the sum of the work done on an object by all forces acting upon the object.

  2. The Work-Energy Theorem • Consider a force applied to an object (ΣF ≠ 0). • Newton’s second law tells us that this net force will produce an acceleration. • Since the object is accelerating, its displacement will change, hence the net force does work.

  3. The Work-Energy Theorem

  4. Kinetic Energy • A form of mechanical energy • Energy due to motion • K = ½ m v2 • K: Kinetic Energy in Joules. • m: mass in kg • v: speed in m/s

  5. The Work-Energy Theorem

  6. The Work-Energy Theorem Wnet = DKE • When net work due to all forces acting upon an object is positive, the kinetic energy of the object will increase. • When net work due to all forces acting upon an object is negative, the kinetic energy of the object will decrease. • When there is no net work acting upon an object, the kinetic energy of the object will be unchanged.

  7. Power • Power is the rate of which work is done. • No matter how fast we get up the stairs, our work is the same. • When we run upstairs, power demands on our body are high. • When we walk upstairs, power demands on our body are lower.

  8. Power • The rate at which work is done. • Pave = W / t • P = dW/dt • P = F • v

  9. Units of Power • Watt = J/s • ft lb / s • horsepower • 550 ft lb / s • 746 Watts

  10. Power Problem Develop an expression for the power output of an airplane cruising at constant speed v in level flight. Assume that the aerodynamic drag force is given by FD = bv2. By what factor must the power be increased to increase airspeed by 25%?

More Related