1 / 23

NAME: _______________________________________ Forces Do Now

NAME: _______________________________________ Forces Do Now. Review-Calculate net force. Four people are pulling on the same 200 kg box with the forces shown. Review-Calculate force. A woman is holding two dogs on a leash.

betrys
Download Presentation

NAME: _______________________________________ Forces Do Now

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. NAME: _______________________________________ ForcesDo Now

  2. Review-Calculate net force • Four people are pulling on the same 200 kg box with the forces shown.

  3. Review-Calculate force • A woman is holding two dogs on a leash. • If each dog pulls with a force of 80 newtons, how much force does the woman have to exert to keep the dogs from moving?

  4. Friction • Frictionis a force that resists the motion of objects or surfaces. • It is the force that two surfaces exert on each other when they rub against each other.

  5. Friction Depends on the: • Types of surfaces • Force between the surfaces • When the hockey puck slides on ice, a thin layer of water between the rubber and the ice allows the puck to slide easily.

  6. Identifying friction forces • Friction is a force, measured innewtonsjust like any other force. • Static frictionkeeps an object atrest from moving.

  7. Identifying friction forces • Sliding frictionis a force that resists the motion of an object moving across a surface. • The object is already moving in sliding friction.

  8. Friction

  9. Friction Friction is greater... • between rough surfaces • when there’s greater force between surfaces (such as more weight)

  10. Reducing the force of friction • Unless a force is constantly applied, friction will slow all motion to a stop eventually. • It is impossible to completely get rid of friction, but it can be reduced.

  11. Useful friction • Friction is also important to anyone driving a car. • Grooved tire treads allow space for water to be channeled away from the road-tire contac point, allowing for more friction in wet conditions.

  12. Useful friction • Shoes are designed to increase the friction between their soles and the ground. Why do you think these shoes increase friction? • Players wearing cleats can apply much greater forces against the ground to help them move and to keep from slipping.

  13. Friction and energy • Friction changes energy of motion into heat energy.

  14. Friction and energy • Each time two moving surfaces touch each other, tiny bits of material are broken off by friction. • Breaking off bits of material uses energy. Friction has affected which pile of stones more?

  15. Video and Practice • http://science.howstuffworks.com/transport/engines-equipment/maglev-train.htm • Answer questions 1(a, b, c, d) and 2 (a and b) with your partner.

  16. Friction Equation Normal force (N) Ff = m Fn Friction force (N) Coefficient of friction

  17. What is the normal force? • A normal force is created whenever an object is in contact with a surface. • The normal force has equal strengthto the force pressing the object into the surface, which is often the object’s weight. The normal force is sometimes called the support force.

  18. G: Given U: Undefined E: Equation S: Substitute S: Solve

  19. A box weighs 100 N, which is the NORMAL FORCE. As the box is pushed horizontally, the coefficient of sliding friction is 0.25. Determine the force of friction resisting the motion. • G: Fn= 100N us=0.25 • U: Ff • E: Ff = usFn • (Frictional Force = Coefficient of Friction x Normal Force) • S: Ff= 0.25 x 100N • S: Ff= 25 N

  20. A steel pot with a weight of 50 N sits on a steel countertop. The coefficient of friction is 0.74. How much force does it take to start the pot sliding? Calculate using friction

  21. A steel pot with a weight of 50 N sits on a steel countertop. The coefficient of friction is 0.74. • How much force does it take to start the pot sliding? G: U: E: S: S:

More Related