Newtonian Forces on Blocks

In summary, two blocks, A (3kg) and B (1kg), are in contact with each other and block A is pushed to the right with a force of 160N when B is let go. The static friction between the two blocks is .50. Block A pushes on B, causing it to be lifted off the surface it was originally on, and only the normal force from A supports it. The normal force exerted by A on B is 40N, and the force of friction on B is 20N. The vertical force exerted by B on A is not mentioned and cannot be determined.
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Homework Statement


Block B (1kg) is held in contact with block A (3kg). When block B is let go, A is pushed to the right with a force of 160N. Static friction is .50 between the 2 blocks.
Block A pushes on B such that B is not touching the surface upon which A is moving on. It's held in the air with only the normal force from A supporting it.
Find the force of friction on Block B, the normal force exerted by A on B, and vertical force exerted by B on A.

Homework Equations


Newtonian forces of friction, gravity, etc

The Attempt at a Solution


For the Normal force of A on B:
to find a: Fnet = 160N = m(A+B)a --> a = 160/4 = 40m/s^2
mAa = F - F(BonA)
FBonA = 160 - (3x40) = 40N = FAonB from Third Law

For Force of Friction on B: Since friction would be working against gravity and there is no vertical motion, wouldn't the force of friction be mBg, its weight?
The Max Ff would be Ff=μN = .50(40)=20N.
Not sure about the vertical force of B on A.
 
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  • #2
Nicolaus said:
For Force of Friction on B: Since friction would be working against gravity and there is no vertical motion, wouldn't the force of friction be mBg, its weight?
How can friction oppose gravity - isn;t this the normal force or did you leave out part of the description?
 

1. What is Newton's first law of motion?

Newton's first law of motion, also known as the law of inertia, states that an object at rest will remain at rest and an object in motion will remain in motion with constant velocity unless acted upon by an external force.

2. What is the formula for calculating force?

The formula for calculating force is F = m x a, where F is force, m is mass, and a is acceleration. This formula is known as Newton's second law of motion.

3. How do Newton's third law of motion affect blocks?

Newton's third law of motion states that for every action, there is an equal and opposite reaction. In the case of blocks, this means that when one block exerts a force on another block, the second block will exert an equal and opposite force on the first block.

4. Can the force of gravity be ignored when calculating Newtonian forces on blocks?

No, the force of gravity cannot be ignored when calculating Newtonian forces on blocks. Gravity is a fundamental force that is always present and can affect the motion of objects, including blocks.

5. What is the difference between static and kinetic friction?

Static friction is the force that resists the motion of an object that is at rest, while kinetic friction is the force that resists the motion of an object that is already in motion. Both types of friction play a role in the movement of blocks.

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