Weight of 2 Blocks on an Incline

In summary, the conversation discusses the correct diagram for Block A in a problem involving a block sliding down an inclined plane while restrained by a string attached to another block resting on top. The professor's solution includes a free body diagram with two frictional forces and a normal force, while the other person's proposed diagram includes two frictional forces up the slope, a normal force from the inclined plane, and a normal force from the block resting on top. The question of whether or not there should be a weight force acting on Block A is also addressed. It is ultimately unclear if there was a misunderstanding between the professor and the other person, as more information is needed to compare their solutions and determine the correct diagram.
  • #1
Sean Smith
2
0

Homework Statement


Block B rests on Block A. Block B is restrained with a string, while Block A slides down the incline. During the time Block A is between Block B and the inclined plane, Block A slides with constant velocity. If the weight of Blocks A and B are both w, and the coefficient of friction is the same between Block A and B and between Block A and the plane, find the value of the coefficient of friction u. [The angle of the incline is 45].

Homework Equations


The professor's solution has a free body diagram for Block A, with two frictional forces and a normal force. This I understand, but he draws weight straight down with magnitude w+w. I thought this was incorrect, as Block A only experiences a Normal force from Block B.

The Attempt at a Solution


The rest of the problem is inconsequential, but my proposed diagram for Block A has 2 frictional forces up the slope, Normal A normal to the slope, Normal B perpendicular to the surface between Blocks A and B, and weight of w.
 

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  • #2
Sean Smith said:
This I understand, but he draws weight straight down with magnitude w+w. I thought this was incorrect, as Block A only experiences a Normal force from Block B.

If block B wasn't there, wouldn't you still draw a force of w acting on block A ?
 
  • #3
Stephen Tashi said:
If block B wasn't there, wouldn't you still draw a force of w acting on block A ?
My bad wording, I thought that Block A would have Weight w and Normal force from B. I drew this in the picture I attached to the original post if you'd like to take a look. (:
 
  • #4
I can't tell anything from that picture.
 
  • #5
The attached picture looks fine, but I presume this is your picture, not your professor's. Without an exact reproduction of what your professor said/drew it will be impossible to tell whether you simply misunderstood. Do you arrive at different answers?
 

Related to Weight of 2 Blocks on an Incline

1. What factors affect the weight of 2 blocks on an incline?

The weight of 2 blocks on an incline is affected by several factors, including the mass of the blocks, the angle of the incline, and the force of gravity. Other factors may include friction and air resistance.

2. How does the angle of the incline impact the weight of the blocks?

The angle of the incline plays a significant role in determining the weight of the blocks. As the angle increases, the force of gravity pulling the blocks down the incline also increases, making the blocks feel heavier. This is due to the component of the force of gravity acting parallel to the incline.

3. Does friction affect the weight of the blocks on the incline?

Friction can impact the weight of the blocks on the incline by either increasing or decreasing it. If there is no friction, the weight of the blocks will be the same as their actual weight. However, if there is friction, it can either increase the weight by making it harder to move the blocks up the incline or decrease the weight by making it easier to move the blocks down the incline.

4. Why is the weight of the blocks different on an incline compared to a flat surface?

The weight of the blocks is different on an incline compared to a flat surface because the force of gravity is acting at an angle on the blocks. This means that only a component of the force is acting in the direction of the incline, while the rest is acting perpendicular to it. This results in a difference in the perceived weight of the blocks.

5. How can the weight of the blocks on an incline be calculated?

The weight of the blocks on an incline can be calculated using the formula W = mg(cosθ), where W is the weight, m is the mass of the blocks, g is the force of gravity, and θ is the angle of the incline. This formula takes into account the component of the force of gravity acting parallel to the incline.

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