Kinetic and Static Friction - AP Physics 1
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What effect does lubrication have on static friction?
What effect does lubrication have on static friction?
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It reduces static friction. Lubrication decreases friction between surfaces.
It reduces static friction. Lubrication decreases friction between surfaces.
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If $f_s = 15 \text{ N}$ and $N = 50 \text{ N}$, find $\text{μ}_s$.
If $f_s = 15 \text{ N}$ and $N = 50 \text{ N}$, find $\text{μ}_s$.
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$\text{μ}_s = 0.3$. Using $\text{μ}_s = f_s/N = 15/50 = 0.3$.
$\text{μ}_s = 0.3$. Using $\text{μ}_s = f_s/N = 15/50 = 0.3$.
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If $f_k = 10 \text{ N}$ and $N = 50 \text{ N}$, find $\text{μ}_k$.
If $f_k = 10 \text{ N}$ and $N = 50 \text{ N}$, find $\text{μ}_k$.
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$\text{μ}_k = 0.2$. Using $\text{μ}_k = f_k/N = 10/50 = 0.2$.
$\text{μ}_k = 0.2$. Using $\text{μ}_k = f_k/N = 10/50 = 0.2$.
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How does surface roughness affect the coefficients of friction?
How does surface roughness affect the coefficients of friction?
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Increases both coefficients. Rougher surfaces create more friction.
Increases both coefficients. Rougher surfaces create more friction.
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Determine the normal force on a $5 \text{ kg}$ object on a flat surface.
Determine the normal force on a $5 \text{ kg}$ object on a flat surface.
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$N = 49 \text{ N}$. Using $N = mg = 5 \times 9.8 = 49$ N.
$N = 49 \text{ N}$. Using $N = mg = 5 \times 9.8 = 49$ N.
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If $f_k = 10 \text{ N}$ and $N = 50 \text{ N}$, find $\text{μ}_k$.
If $f_k = 10 \text{ N}$ and $N = 50 \text{ N}$, find $\text{μ}_k$.
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$\text{μ}_k = 0.2$. Using $\text{μ}_k = f_k/N = 10/50 = 0.2$.
$\text{μ}_k = 0.2$. Using $\text{μ}_k = f_k/N = 10/50 = 0.2$.
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If an object is moving at constant speed, what can be said about friction?
If an object is moving at constant speed, what can be said about friction?
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Kinetic friction equals the applied force. No net force means friction balances applied force.
Kinetic friction equals the applied force. No net force means friction balances applied force.
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Find kinetic friction if $\text{μ}_k = 0.1$ and $N = 250 \text{ N}$.
Find kinetic friction if $\text{μ}_k = 0.1$ and $N = 250 \text{ N}$.
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$f_k = 25 \text{ N}$. Using $f_k = \text{μ}_k N = 0.1 \times 250 = 25$ N.
$f_k = 25 \text{ N}$. Using $f_k = \text{μ}_k N = 0.1 \times 250 = 25$ N.
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What is the primary force opposing motion on a flat surface?
What is the primary force opposing motion on a flat surface?
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Friction. Friction opposes relative motion between surfaces.
Friction. Friction opposes relative motion between surfaces.
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What does $\text{μ}$ depend on?
What does $\text{μ}$ depend on?
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Material properties of surfaces. Coefficient depends on surface materials and conditions.
Material properties of surfaces. Coefficient depends on surface materials and conditions.
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If $\text{μ}_k = \text{μ}_s$, what can be inferred about motion?
If $\text{μ}_k = \text{μ}_s$, what can be inferred about motion?
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Frictional resistance is constant during motion. Same friction force whether moving or stationary.
Frictional resistance is constant during motion. Same friction force whether moving or stationary.
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Identify the type of friction that occurs when an object is at rest.
Identify the type of friction that occurs when an object is at rest.
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Static friction. Acts on objects that aren't sliding.
Static friction. Acts on objects that aren't sliding.
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Find the kinetic friction if $\text{μ}_k = 0.3$ and $N = 70 \text{ N}$.
Find the kinetic friction if $\text{μ}_k = 0.3$ and $N = 70 \text{ N}$.
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$f_k = 21 \text{ N}$. Using $f_k = \text{μ}_k N = 0.3 \times 70 = 21$ N.
$f_k = 21 \text{ N}$. Using $f_k = \text{μ}_k N = 0.3 \times 70 = 21$ N.
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What does the symbol $f_k$ represent?
What does the symbol $f_k$ represent?
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The force of kinetic friction. Standard notation for kinetic friction force.
The force of kinetic friction. Standard notation for kinetic friction force.
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What does the symbol $f_s$ represent?
What does the symbol $f_s$ represent?
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The force of static friction. Standard notation for static friction force.
The force of static friction. Standard notation for static friction force.
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Which option best describes friction between a sled and snow while sliding?
Which option best describes friction between a sled and snow while sliding?
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Kinetic friction. Sled slides continuously across the surface.
Kinetic friction. Sled slides continuously across the surface.
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Find static friction if $\text{μ}_s = 0.6$ and $N = 200 \text{ N}$.
Find static friction if $\text{μ}_s = 0.6$ and $N = 200 \text{ N}$.
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$f_s \text{ (max)} = 120 \text{ N}$. Using $f_s = \text{μ}_s N = 0.6 \times 200 = 120$ N.
$f_s \text{ (max)} = 120 \text{ N}$. Using $f_s = \text{μ}_s N = 0.6 \times 200 = 120$ N.
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What happens to kinetic friction as the angle of an inclined plane increases?
What happens to kinetic friction as the angle of an inclined plane increases?
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Kinetic friction remains constant regardless of angle. Kinetic friction magnitude doesn't change with angle.
Kinetic friction remains constant regardless of angle. Kinetic friction magnitude doesn't change with angle.
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What is the effect of increasing the mass on normal force?
What is the effect of increasing the mass on normal force?
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Normal force increases. More mass creates larger normal force.
Normal force increases. More mass creates larger normal force.
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Identify the friction type when pushing an object that does not move.
Identify the friction type when pushing an object that does not move.
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Static friction. Object remains at rest, so static friction acts.
Static friction. Object remains at rest, so static friction acts.
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What does a higher coefficient of friction indicate?
What does a higher coefficient of friction indicate?
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Greater resistance to motion. Higher coefficients mean more frictional force.
Greater resistance to motion. Higher coefficients mean more frictional force.
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What effect does lubrication have on kinetic friction?
What effect does lubrication have on kinetic friction?
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It reduces kinetic friction. Lubrication decreases friction between surfaces.
It reduces kinetic friction. Lubrication decreases friction between surfaces.
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What is the unit of measurement for the coefficients of friction?
What is the unit of measurement for the coefficients of friction?
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Dimensionless (no units). Coefficients are ratios of forces.
Dimensionless (no units). Coefficients are ratios of forces.
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Find the maximum static friction if $\text{μ}_s = 0.4$ and $N = 50 \text{ N}$.
Find the maximum static friction if $\text{μ}_s = 0.4$ and $N = 50 \text{ N}$.
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$f_s \text{ (max)} = 20 \text{ N}$. Using $f_s = \text{μ}_s N = 0.4 \times 50 = 20$ N.
$f_s \text{ (max)} = 20 \text{ N}$. Using $f_s = \text{μ}_s N = 0.4 \times 50 = 20$ N.
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Define the coefficient of static friction.
Define the coefficient of static friction.
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The ratio of maximum static friction force to the normal force. Shows how friction scales with normal force for stationary objects.
The ratio of maximum static friction force to the normal force. Shows how friction scales with normal force for stationary objects.
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What happens to static friction as the angle of an inclined plane increases?
What happens to static friction as the angle of an inclined plane increases?
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Static friction increases until the object starts to move. Adjusts to prevent sliding up to its maximum.
Static friction increases until the object starts to move. Adjusts to prevent sliding up to its maximum.
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Which option best describes friction between tires and a road while driving?
Which option best describes friction between tires and a road while driving?
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Static friction. Tires grip the road without sliding.
Static friction. Tires grip the road without sliding.
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Find the normal force if $m = 10 \text{ kg}$ and $g = 9.8 \text{ m/s}^2$ on a flat surface.
Find the normal force if $m = 10 \text{ kg}$ and $g = 9.8 \text{ m/s}^2$ on a flat surface.
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$N = 98 \text{ N}$. Using $N = mg = 10 \times 9.8 = 98$ N.
$N = 98 \text{ N}$. Using $N = mg = 10 \times 9.8 = 98$ N.
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Find the kinetic friction if $\text{μ}_k = 0.2$ and $N = 100 \text{ N}$.
Find the kinetic friction if $\text{μ}_k = 0.2$ and $N = 100 \text{ N}$.
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$f_k = 20 \text{ N}$. Using $f_k = \text{μ}_k N = 0.2 \times 100 = 20$ N.
$f_k = 20 \text{ N}$. Using $f_k = \text{μ}_k N = 0.2 \times 100 = 20$ N.
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Identify the friction type when an object slides down a slope.
Identify the friction type when an object slides down a slope.
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Kinetic friction. Object is moving, so kinetic friction acts.
Kinetic friction. Object is moving, so kinetic friction acts.
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