Static frictions and moving boxes on top of a box

In summary, the conversation discusses solving question 4 using Newton's second law and how to incorporate the masses of the box and cart in the equation. It is determined that the mass of the box does not affect the force applied by the person.
  • #1
okgo
61
0

Homework Statement



http://www.screencast.com/users/trinhn812/folders/Jing/media/d77fab7d-ece6-4c9c-be65-bf41f94770fd

Homework Equations



I got the right answers doing the work shown, but I don't understand the logic of how I solved question 4.

The Attempt at a Solution

 
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  • #2
hi okgo! :wink:

you need to use good ol' Newton's second law (F = ma) twice …

show us what you get :smile:
 
  • #3
hmm so far..
m= mass of box and M=mass of cart. I assume the acceleration of the box and cart is the same.

F(box)=force(friction)=umg=ma
ug=a

F(cart)=force done by you=Ma
Substitute ug=a into the equation.
u*g*M=Force so mass of the box doesn't matter?
 
  • #4
okgo said:
F(cart)=force done by you=Ma

Is that for the cart M or for both M and m?
 
  • #5
ohh I didn't include that. Thanks, it makes sense!
 

1. What is static friction?

Static friction is the force that prevents an object from moving when it is in contact with another surface. It acts parallel to the surface and opposite to the direction of motion.

2. How does static friction affect moving boxes on top of a box?

Static friction plays a crucial role in keeping the boxes on top of a box in place. It provides the necessary force to prevent the boxes from slipping off due to the weight and gravity acting on them.

3. What factors affect the amount of static friction?

The amount of static friction depends on the nature of the surfaces in contact, the normal force between them, and any external forces acting on the system. It also varies with the roughness and texture of the surfaces.

4. Can static friction be greater than kinetic friction?

Yes, static friction can be greater than kinetic friction. This is because static friction adjusts itself to match the applied force, whereas kinetic friction remains relatively constant.

5. How can we reduce static friction between surfaces?

Static friction can be reduced by using lubricants, such as oil or grease, between the surfaces. It can also be reduced by applying a force in the opposite direction of motion, which slightly lifts the object and reduces the contact area between the surfaces.

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