Learning Path
Question & Answer1
Understand Question2
Review Options3
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Explore TopicChoose the Best Answer
A
The normal force decreases and friction decreases.
B
The normal force remains constant while friction decreases.
C
The normal force increases and friction increases.
D
The normal force remains constant while friction increases.
Understanding the Answer
Let's break down why this is correct
Answer
When the surface gets hotter the block and the floor expand slightly, which can reduce the contact area and therefore lower the normal force that the floor exerts on the block. Because the normal force is the weight minus any small lift caused by expansion, the frictional force, which equals the coefficient of kinetic friction times the normal force, also drops. The coefficient of kinetic friction itself tends to decrease with temperature, so the frictional force decreases even more. For example, if the normal force falls from 147 N to 140 N and the coefficient drops from 0. 4 to 0.
Detailed Explanation
The block’s weight is 15 kg × 9.8 m/s², so the normal force stays at 147 N even when the surface gets hot. Other options are incorrect because Some think heat makes the block lighter, but weight is a product of mass and gravity, which is unchanged; Heat does not make the block press harder on the floor.
Key Concepts
Normal Force
Temperature Effects on Friction
Surface Roughness Impact on Friction
Topic
Friction Forces Analysis (Part 3)
Difficulty
hard level question
Cognitive Level
understand
Practice Similar Questions
Test your understanding with related questions
1
Question 1When a block of metal is initially at rest on a heated surface, what effect does increasing the temperature have on the static friction coefficient compared to the kinetic friction coefficient once the block starts sliding?
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2
Question 2When a smooth metal block is placed on a rough surface, how does the surface roughness affect the normal force required to maintain static equilibrium before the block begins to slide?
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3
Question 3If the temperature of a surface increases significantly, how would this most likely affect the normal force and the frictional force acting on an object resting on that surface?
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4
Question 4If a 10 kg block is sliding across a horizontal surface with a coefficient of kinetic friction of 0.3, what is the kinetic frictional force acting on the block?
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5
Question 5You are analyzing a scenario where two blocks are placed on a surface, Block A has a mass of 5 kg and Block B has a mass of 0.4 kg. Both blocks experience different frictional forces against the same surface. Classify the following statements into correct categories regarding their friction coefficients: 1) The friction coefficient of Block A is greater than that of Block B. 2) The frictional force on Block B can be considered negligible compared to Block A. 3) The friction coefficient depends solely on the mass of the block. 4) The surface material affects the friction coefficient regardless of mass. Which statements belong to the category of 'Correct Understanding of Friction Coefficients'?
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6
Question 6A 5 kg block is sliding on a horizontal surface with a coefficient of kinetic friction of 0.3. If the block is pushed with a force of 20 N to the right, what is the final velocity of the block after 2 seconds, assuming it starts from rest? Consider both Newton's Laws and the conservation of momentum in your calculations.
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7
Question 7A 5 kg block is sliding on a horizontal surface with a coefficient of kinetic friction of 0.3. If the block is pushed with a force of 20 N to the right, what is the final velocity of the block after 2 seconds, assuming it starts from rest? Consider both Newton's Laws and the conservation of momentum in your calculations.
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