Two boxes connected to a string over an ideal pulley?

In summary: In this case, F_{normal} is equal to the weight of the block, which is m_1g. Therefore, ffriction = μm_1g = 0.4*3*9.81 = 11.724N. The force of gravity is equal to the weight of the block multiplied by the sine of the angle of inclination, which is 30 degrees. So fgrav = m_1gsin(30) = 3*9.81*sin(30) = 14.715N. Now, using Newton's second law, we can set the sum of the forces equal to the mass of block A times its acceleration. Since we want the block to start sliding, the
  • #1
algar32
89
1

Homework Statement


Two blocks are connected by a string that goes over an ideal pulley as shown in the figure and pulls on block A parallel to the surface of the plane. Block A has a mass of 3.00 kg and can slide along a rough plane inclined 30.0° to the horizontal. The coefficient of static friction between block A and the plane is 0.400. What mass should block B have in order to start block A sliding up the plane?


Homework Equations


box A- sum of x & sum of y
box B- sum of y
plug into each other



The Attempt at a Solution


m2=(ms*m1*sin(theta)+m1*cos(theta)
=3.198


Thanks.
 
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  • #2
First of all. What are all the forces acting upon block A?
 
  • #3
tal444 said:
First of all. What are all the forces acting upon block A?

The forces acting on block A are static friction, fnormal, gravity, and ftension.
 
  • #4
Yes. So the friction force and force of gravity are preventing the block from sliding up the ramp. What's next?
 
  • #5
tal444 said:
Yes. So the friction force and force of gravity are preventing the block from sliding up the ramp. What's next?

ffriction = -.4*9.81*3
fgrav= -sin30*9.81*3
ftension =m*9.81

ffriction +fgrav = ftension

Not sure which part i messed up
 
Last edited:
  • #6
algar32 said:
ffriction = -.4*9.81*3

Friction force is equal to μF[itex]_{normal}[/itex].
 

FAQ: Two boxes connected to a string over an ideal pulley?

What is an ideal pulley?

An ideal pulley is a simple machine that consists of a wheel with a grooved rim and a rope or cable that runs along the groove. It is considered ideal because it has no friction, mass, or inertia, meaning that it does not affect the motion of the objects it is connected to.

How are the two boxes connected to the string over the ideal pulley?

The string is wrapped around the grooved rim of the pulley and tied to both boxes. This creates a system where the motion of one box is directly related to the motion of the other box.

What is the purpose of connecting two boxes with a string over an ideal pulley?

This setup is commonly used in physics experiments to study the principles of tension, acceleration, and energy conservation. It allows for the manipulation and measurement of these variables in a controlled and simplified manner.

How does the motion of the two boxes relate to each other?

The motion of the two boxes are directly related to each other through the string and the pulley. This means that if one box moves, the other box will also move in the opposite direction with the same magnitude of motion.

What are some real-life applications of the two boxes connected to a string over an ideal pulley setup?

This setup can be found in various machines and devices, such as elevators, cranes, and exercise equipment. It is also commonly used in physics classrooms to demonstrate concepts such as Newton's laws of motion and mechanical advantage.

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