Solving Friction & Gravity Homework: Acceleration of Blocs

In summary, the conversation discusses the problem of two blocks with the same mass connected by a rope and initially at rest, with the same friction coefficients. The question is posed of what the acceleration of the blocks would be if the static coefficient of friction is 0.25 and the kinetic coefficient of friction is 0.2. The conversation also includes mentions of Newton's second law and the friction formula, as well as the need for as many equations as unknowns to solve the problem.
  • #1
astrololo
200
3

Homework Statement



Two blocs with the same mass have the same rope which links them. The friction coefficients are the same whatever the surface. The blocs are initialy stationary and we let them move. What is the module of the acceleration of the blocs if static coefficient of friction =0,25
Cinetic coefficient of friction = 0,2

Homework Equations



Newton's second law. Sum forces = ma
and
fs or c = u* n (friction formula)

The Attempt at a Solution


I don't know what to do to be honest. I know what forces we have, I know how to write Newton's formula for each object and I get a total of 4 formulas for NEwton's second law. But after that, where do I go ?
 
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  • #2
Where are the blocks? Why should they move at all? There is something missing.
astrololo said:
I don't know what to do to be honest. I know what forces we have, I know how to write Newton's formula for each object and I get a total of 4 formulas for NEwton's second law. But after that, where do I go ?
They are connected by a rope, so their distance cannot increase.
 
  • #3
mfb said:
Where are the blocks? Why should they move at all? There is something missing.
They are connected by a rope, so their distance cannot increase.
I'm REALLY sorry, I forgot this : http://imgur.com/Dw7XvAE
 
  • #4
You should get as many equations as unknowns, so you can solve the problem.
 
  • #5
mfb said:
You should get as many equations as unknowns, so you can solve the problem.
Ok, so how many ? 2 in 2 ?
 
  • #6
Draw a free body diagram for both blocks and match all the forces acting on the y and x axis
 
  • #7
astrololo said:
Ok, so how many ? 2 in 2 ?
That depends on how you set up the equations. Some constraints can be included directly in the choice of variables.
It would help to show your equations.
 

1. What is friction and how does it affect the acceleration of blocks?

Friction is a force that opposes the motion of objects. It is caused by the contact between two surfaces and can vary depending on the type of surfaces and the force applied. Friction can decrease the acceleration of blocks by slowing down their motion.

2. How do you calculate the acceleration of blocks on an inclined plane?

The acceleration of blocks on an inclined plane can be calculated using the formula a = g sinθ, where a is the acceleration, g is the acceleration due to gravity (9.8 m/s²), and θ is the angle of the inclined plane.

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

Static friction is the force that prevents two surfaces from sliding against each other when they are at rest. Kinetic friction, on the other hand, is the force that opposes the motion of two surfaces that are in contact and moving relative to each other. Kinetic friction is usually lower than static friction.

4. How does the mass of a block affect its acceleration?

The mass of a block does not directly affect its acceleration. According to Newton's Second Law of Motion, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This means that if the force acting on the block is constant, the acceleration will not change regardless of the mass of the block.

5. Can you have negative acceleration in the case of friction?

Yes, it is possible to have negative acceleration in the case of friction. This occurs when the force of friction is greater than the applied force, causing the object to decelerate. Negative acceleration is also known as deceleration or retardation.

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