Calculating Acceleration of Blocks on a Ramp

In summary, the conversation discusses a problem involving three blocks, A, B, and C, with weights of 51 N, 23 N, and an unknown weight for C. The minimum weight of C to keep A from sliding is determined to be 4.8, but the acceleration of block A when C is suddenly lifted off is incorrect. The correct equation for this situation is Fxnet= T-UkFn=ma, and solving for a yields an answer of 0.23.
  • #1
shell4987
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0

Homework Statement


In Fig. 6-35, blocks A and B have weights of 51 N and 23 N, respectively. (a) Determine the minimum weight of block C to keep A from sliding if μs between A and the table is 0.23. (b) Block C suddenly is lifted off A. What is the acceleration of block A if μk between A and the table is 0.12?
**image is attached**

Homework Equations


fxnet= T-fs=ma
fymet= FN-Wc-Wa=0

fxnet=T-UkFn=ma

The Attempt at a Solution



I completed part (a) and got 4.8 to be the answer, however, I didnt get part (b), I tried to use the tension I got from part (a) and put it in the 3rd equation above and got -14,472 which is obviously not correct. Can anyone tell me what I'm doing wrong?
 

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  • #2
The tension is not the same once things start accelerating. You'll have to set up equations for both masses and solve for the acceleration (and new tension).
 
  • #3
Okay, I did that... the second two equations were Fxnet= T-Uk(WA)=ma and Fynet= Wb-T=ma and when I added them together I got Wb - Uk(Wa)=(ma + mb)a and then solved for a and got 0.23 for the answer, and it was yet again wrong. What am I doing that's not right again?
 
  • #4
Be sure when calculating ma + mb that you are adding the masses and not the weights.
 

Related to Calculating Acceleration of Blocks on a Ramp

What is the basic concept of "Blocks on a Ramp Question"?

The "Blocks on a Ramp Question" is a physics problem that involves a block moving on an inclined plane or ramp, subject to gravity and friction forces.

What are the key factors that affect the motion of the block in this problem?

The key factors that affect the motion of the block are the angle of the ramp, the mass of the block, and the coefficient of friction between the block and the ramp.

How do you calculate the net force acting on the block?

The net force acting on the block can be calculated by using Newton's Second Law, which states that the net force is equal to the mass of the object multiplied by its acceleration. In this problem, the acceleration is affected by the forces of gravity and friction.

What is the relationship between the angle of the ramp and the acceleration of the block?

The angle of the ramp and the acceleration of the block have an inverse relationship. As the angle of the ramp increases, the acceleration of the block decreases, and vice versa.

How does the coefficient of friction affect the motion of the block?

The coefficient of friction determines the amount of friction force acting on the block, which in turn affects its acceleration. A higher coefficient of friction will result in a slower acceleration, while a lower coefficient of friction will result in a faster acceleration.

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