Block of mass Rotational Problem

In summary, two blocks of masses 2.00 kg and 6.00 kg are connected by a string over a pulley with a mass of 10.0 kg and a radius of 0.250 m. The blocks are on a fixed block-wedge and have a coefficient of kinetic friction of 0.360. By solving for the torque using the equation T1 + T2 = I(a/R^2), the acceleration of the blocks and the tensions in the string can be determined. It is important to note that the direction of the torque can be determined using the right-hand rule, where clockwise is negative and counterclockwise is positive.
  • #1
AriAstronomer
48
1

Homework Statement


A block of mass m1 = 2.00 kg and a block of mass m 2 =
6.00 kg are connected by a massless string over a pulley
in the shape of a disk having radius R = 0.250 m and
mass M = 10.0 kg. These blocks are allowed to move on
a fixed block – wedge of angle 30.0°, as shown in
Figure P10.39. The coefficient of kinetic friction for
both blocks is 0.360. Draw free-body diagrams of both
blocks and of the pulley. Determine (a) the acceleration
of the two blocks and (b) the tensions in the string on
both sides of the pulley.

Diagram: http://www.webassign.net/pse/pse6_p10-37.gif

Homework Equations





The Attempt at a Solution


Now I know how to solve this problem, the only thing I'm stuck on, is the pulley. I know that you have to make a substitution for the acceleration using:
Torque = (T1 + T2)R = I(alpha)
T1 + T2 = I(a/R^2).
The only thing I don't understand is why T1 is negative and T2 is positive (T1 being the tension affecting m1, and T2 affecting T2). By R.H.R, torque1 = T1xR = out of page, which I just assumed should be positive, and thus T2 should be negative, but I only get the right answer if I have T2 - T1 = I(a/R^2), and not T1 - T2 = I(a/R^2). I don't think I'm missing a sign anywhere else, this is kind of a popular problem, and have compared my solutions to others.

Any help would be appreciated.
Ari
 
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  • #2
nvm. Clockwise = negative
 

FAQ: Block of mass Rotational Problem

1. What is a "Block of mass Rotational Problem"?

A "Block of mass Rotational Problem" is a type of physics problem that involves a block of mass rotating around a fixed axis. This problem often requires the use of rotational kinematics and dynamics equations to determine the motion and forces acting on the block.

2. How do I approach solving a "Block of mass Rotational Problem"?

To solve a "Block of mass Rotational Problem", you will first need to identify the given information and what is being asked in the problem. Then, you can apply the rotational kinematics and dynamics equations to determine the unknown variables. It is also helpful to draw a free body diagram and consider any relevant physical principles.

3. What are some common mistakes when solving a "Block of mass Rotational Problem"?

Some common mistakes when solving a "Block of mass Rotational Problem" include not considering the correct axis of rotation, forgetting to include all relevant forces (such as tension or friction), and mixing up the sign conventions for rotational variables (such as angular velocity and angular acceleration).

4. Are there any tricks or shortcuts for solving a "Block of mass Rotational Problem"?

While there are no specific tricks or shortcuts for solving a "Block of mass Rotational Problem", it can be helpful to break the problem down into smaller steps and consider the physical meaning of the variables and equations being used. It is also important to carefully check your work and make sure all units are consistent.

5. How can I use "Block of mass Rotational Problems" in real-life applications?

"Block of mass Rotational Problems" are commonly used in engineering and physics to analyze the motion and forces of rotating objects, such as gears, wheels, and pulleys. They can also be applied to real-life situations, such as calculating the torque and angular acceleration of a wind turbine or understanding the dynamics of a spinning top.

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