Finding Acceleration and Tension, With Friction

In summary, the conversation involved solving a physics problem involving the coefficient of kinetic friction between two blocks on a frictionless surface. The solution involved drawing free-body diagrams, using equations for acceleration and gravity, and solving for tension in the strings. A mistake was made in the final calculation, resulting in an incorrect answer for T1.
  • #1
VACA
16
0

Homework Statement


In figure P4.52 (below), the coefficient of kinetic friction between two blocks shown is 0.30. The surface of the table and the pulleys are frictionless. (a) Draw a free-body diagram for each block. (b) Determine the acceleration of each block. (c) Find the tension in the strings.

p4_56.gif



Homework Equations


Since all accelerations are equal:
-a2 = a3 = -a10

Also, a = F/m
And for gravity: Fg=m (in kg)*9.8


The Attempt at a Solution



For the force diagram I know that the 2kg block will have T1 pulling it to the left and friction pulling it to the right. The 3kg block will have T2 pulling it to the right and friction and T1 pulling to the left. And the 10kg ball, sphere, whatever, has T2 pulling upward and gravity pulling downward.

Fk is 5.88N since Fn is 19.6N (0.3*19.6).
And Fg is 98N.

- (5.88N - T1) / 2kg = (T2 - T1 - 5.88N) / 3kg = - (T2 - 98N) / 10kg Got rid of my fractions, LCD of 30...

15T1 - 88.2N = 10T2 - 10T1 -58.8N = 294N - 3T2 Used the first two equations to solve for T2

2.5T1 - 2.94N = T2 Plugged into the last 2 equations and ended up getting...

25T1 - 29.4N - 10T1 - 58.8N = 294N - 7.5T1 + 88.2N

T1 = 20.906N


The correct answer for T1 is 17N. I've looked over my work and couldn't find a mistake in my math, though I'm sure there is. I need help figuring out where I messed up.

I hope this isn't just some dumb mistake because I've spent so long on this single problem.

Thanks in advance.
 
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  • #2
VACA said:
25T1 - 29.4N - 10T1 - 58.8N = 294N - 7.5T1 + 88.2N


All is Ok except for a small mistake. Last number is not 88.2 but 8.82.
 

FAQ: Finding Acceleration and Tension, With Friction

How do you find the acceleration of an object with friction?

To find the acceleration of an object with friction, you can use Newton's Second Law of Motion, which states that the net force acting on an object is equal to its mass multiplied by its acceleration. In this case, the net force would include the force of friction. By rearranging the equation, you can solve for the acceleration.

What is the role of friction in determining tension?

Friction plays a crucial role in determining tension in a system. The force of friction acts in the opposite direction of motion, which can impact the overall tension in a system. In some cases, the force of friction may increase the tension, while in others it may decrease it. It is important to consider friction when calculating tension in a system.

How can you account for friction when calculating acceleration and tension?

To account for friction when calculating acceleration and tension, you can use the coefficient of friction. This value represents the amount of friction between two surfaces and can be used in equations to adjust for the impact of friction. It is important to know the coefficient of friction for the surfaces in question to accurately account for it in calculations.

Can you have a negative acceleration or tension due to friction?

Yes, it is possible to have a negative acceleration or tension due to friction. This occurs when the force of friction is greater than the applied force, causing the object to decelerate or the tension in the system to decrease. Negative acceleration and tension can also occur when there are opposing forces acting on the object, such as in a tug-of-war situation.

How does the weight of an object affect the acceleration and tension in a system with friction?

The weight of an object does not directly affect the acceleration and tension in a system with friction. However, the weight of an object does contribute to the overall force acting on the object, which can impact the acceleration and tension. For example, a heavier object may experience a greater force of friction, leading to a lower acceleration and tension compared to a lighter object in the same system.

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