APPLICATIONS OF NEWTON'S LAWS

1K10.30 WALKING SPOOL
1K20.10 FRICTION OF DIFFERENT SURFACES
1K20.30 STATIC VS SLIDING SURFACES
1K20.35 FRICTION ON INCLINED PLANE
1K30.10 BED OF NAILS



1K10.30 Walking the Spool

Pull string at various angles to make spool move forward with rotation, slide without rotating, or move backwards with rotation.

img_0489walkspol.jpg

Setup Requirements: Off the shelf

 

Equations: Standard textbook example. The cosine of the angle string makes with horizontal at slide without rotating position = r/R where r is the inner radius. 

 

Safety Issues: none



1K20.10 Friction of Different Surfaces

Pull weights on various surfaces across desktop.Use a spring scale to show how friction depends on roughness of surface.

1k20_30.jpg

Setup Requirements: Wood, sandpaper,metal and bricks available.

 

Equations: F= coefficient of friction x normal force

 

Safety Issues: none



1K20.30 Static vs. Sliding Friction

Using a spring scale and block you can show that static friction is greater than sliding fricton. Coefficient of sliding friction < coefficient of static friction for a given surface.

!1k20_30.jpg

Setup Requirements: Minimal

 

Equations: Force = coefficient of friction x normal force.

 

Safety Issues: none



1K20.35 Friction on Inclined Plane

The coefficient of friction can be measured by increasing the angle until object starts to slide.

!1K20_35.JPG

Setup Requirements: Off the shelf

 

Equations: By splitting the force of gravity into normal component and component along the incline it is found that coefficient of static friction = tangent of angle.

 

Safety Issues: none



1K30.10 Bed of Nails (Pressure)

Lie down carefully on bed of nails. Spreading your weight out reduces the pressure exerted by any one nail. Compare to putting weight on small heels of high heeled shoes.

!1K30_10.JPG 

Setup Requirements: Off the shelf

 

Equations: P = F/A

 

Safety Issues: Holes in you and your clothes.