Math Problem Statement
A large block with mass is on a frictionless horizontal surface.𝑚1 = 50 𝑘𝑔 Another smaller block with mass is placed on top of the first block as shown.𝑚2 = 20 𝑘𝑔 The coefficients of friction between the two blocks are and . A forceμ𝑠 = 0. 60 μ𝑘 = 0. 30 is applied to the top block at an angle below the horizontal as shown.𝑃 = 200 𝑁 θ = 30◦ Find the acceleration of each block. (Hint: First determine whether or not the top block slides relative to the bottom block).
Solution
To determine the accelerations of the blocks (and whether the top block slides), we'll need to analyze the forces acting on each block and apply Newton's second law of motion. Here's a step-by-step approach:
Step 1: Analyze forces on the top block ()
- The applied force has a horizontal component and a vertical component .
- The gravitational force acting on the block is .
- The normal force exerted by the bottom block on the top block adjusts for and the vertical component of :
Step 2: Determine if the top block slides
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Calculate the maximum static friction force:
-
Check if exceeds this maximum static friction force: If , the top block does not slide. Otherwise, it slides.
Step 3a: Top block does not slide
If the top block does not slide, both blocks move together with the same acceleration :
- The friction force on acts to the left and there is no horizontal acceleration on .
Using Newton's second law for both blocks together:
-
Total mass
-
Total force
Step 3b: Top block slides
If the top block slides, it means . In this case, the friction is kinetic friction.
The accelerations are separate:
For :
-
Kinetic friction force acting backward:
For :
-
Force due to friction acting forward:
Conclusion
Calculations:
Using values, we find:
- Maximum static friction
Since , the block slides.
Thus:
- Kinetic friction
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Math Problem Analysis
Mathematical Concepts
Newton's Laws of Motion
Static and Kinetic Friction
Trigonometry in Physics
Force Analysis
Formulas
P_x = P * cos(θ)
P_y = P * sin(θ)
f_max = μs * N
a = F / m
f_k = μk * N
Theorems
Newton's Second Law of Motion (F = ma)
Concept of Frictional Force
Suitable Grade Level
Grades 11-12
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