1 / 15

Aim: How can we explain forces at an angle?

Aim: How can we explain forces at an angle?. x = 5 N. x. Do Now: Solve for the x and y components:. 30°. y. 10 N. x = 8.7 N. Why do crazy football coaches say to get low?. Demo http://www.youtube.com/watch?v=eE6x1rfogIU&feature=related

eric-ayala
Download Presentation

Aim: How can we explain forces at an angle?

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 explain forces at an angle? x = 5 N x Do Now: Solve for the x and y components: 30° y 10 N x = 8.7 N

  2. Why do crazy football coaches say to get low? • Demo • http://www.youtube.com/watch?v=eE6x1rfogIU&feature=related • If force is at an angle, some component of the force is in the x direction and some is in the y

  3. Forces at an Angle 50 N • A 12 kg box is pulled across a table with a force of 50 N at an angle of 40o above the horizontal. • Draw a free body diagram • Write a net force equation in the x and y direction • What is the normal force? • If the box moves at a constant velocity, what is the force of friction? • What is the coefficient of friction? 40o 12 kg

  4. Question 2 • A small child pulls a 25 kg wagon with 30 N of force over a frictionless surface. The angle that the handle makes with the ground is 27o • What is the horizontal component of the force? • What is the vertical component of the force? • Write a net force equation in the x and y direction • What is the acceleration of the wagon • If the wagon starts from rest, how far does the child go in 4 seconds?

  5. Normal Force Do you remember where the normal force is directed? What if the plane is inclined?

  6. On an incline:

  7. The problem with an incline: The object moves along the plane y y Everything would need to be resolved into x and y components That’s a lot of sins and cosines Solution – rotate the x and y axis x Fg x

  8. This way, only Fg needs to be resolved into x and y components - F║ and F┴

  9. FN How can we solve for F║ and F┴ FII Mathematically, these θ’s are equal θ F θ Fg = mg

  10. At rest or moving with a constant velocity: FF = ? FF = F║ FF = Fgsinθ FF = mgsinθ FN FN = ? FN = F┴ FN = Fgcosθ FN = mgcosθ FF FII θ F θ Fg

  11. FN As θ increases, FII increases, so Fnet increases, and the object accelerates faster On a frictionless incline: FNet = ma F║ = ma Fgsinθ = ma mgsinθ = ma gsinθ = a FF FII θ F θ Fg

  12. On a surface with friction… • The force of friction decreases as the angle increases since: Remember: cos(90o)= 0 and cos(0o) = 1 The higher the angle, the lower the value of cosine

  13. FII = Fgsinθ FII = mgsinθ FII = (50 kg)(9.8 m/s2)sin(25o) FII = 207 N F = Fgcosθ F = mgcosθ F = (50 kg)(9.8 m/s2)cos(25o) F = 444 N Ex: A 50 kg object rests on a table that is inclined 25o from the horizontal. (a) Determine the components of gravity acting on the object. (b) What is the Normal force? FN = F┴ = 444 N

  14. What is the force of friction if the object is at rest? FF = F║ FF = 207 N Assume the incline is now frictionless What is the acceleration down the incline? FNet = ma F║ = ma 207 N = (50 kg)a a = 4.14 m/s2

  15. What is the coefficient of static friction? FF = µFN 207 N = µ(444 N) µ = 0.47 How far will the object travel in 5 s? d = vit + ½at2 d = (0 m/s)(5 s) + ½(4.14 m/s2)(5 s)2 d = 51.75 m

More Related