Motion and Energy Transfer - Middle School Physical Science
Card 1 of 25
What is kinetic energy in terms of mass and speed?
What is kinetic energy in terms of mass and speed?
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$KE=\frac{1}{2}mv^2$. KE depends on mass and the square of velocity.
$KE=\frac{1}{2}mv^2$. KE depends on mass and the square of velocity.
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What is the relationship between net work and change in kinetic energy?
What is the relationship between net work and change in kinetic energy?
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$W_{net}=\Delta KE$. Work-energy theorem: net work equals change in kinetic energy.
$W_{net}=\Delta KE$. Work-energy theorem: net work equals change in kinetic energy.
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What does positive net work on an object imply about its speed?
What does positive net work on an object imply about its speed?
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Kinetic energy increases; speed increases. Positive work adds energy, increasing velocity.
Kinetic energy increases; speed increases. Positive work adds energy, increasing velocity.
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What does negative net work on an object imply about its speed?
What does negative net work on an object imply about its speed?
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Kinetic energy decreases; speed decreases. Negative work removes energy, reducing velocity.
Kinetic energy decreases; speed decreases. Negative work removes energy, reducing velocity.
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What is the formula for work done by a constant force parallel to motion?
What is the formula for work done by a constant force parallel to motion?
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$W=Fd$. Work equals force times displacement when parallel.
$W=Fd$. Work equals force times displacement when parallel.
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Which sign describes work by friction on a sliding object moving forward?
Which sign describes work by friction on a sliding object moving forward?
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Negative work. Friction opposes motion, doing negative work.
Negative work. Friction opposes motion, doing negative work.
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What energy transfer occurs when friction slows an object on a surface?
What energy transfer occurs when friction slows an object on a surface?
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Kinetic energy transfers to thermal energy. Friction converts motion energy to heat.
Kinetic energy transfers to thermal energy. Friction converts motion energy to heat.
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What happens to kinetic energy when an object speeds up due to a push?
What happens to kinetic energy when an object speeds up due to a push?
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Energy transfers into the object; $KE$ increases. Applied force does positive work, adding KE.
Energy transfers into the object; $KE$ increases. Applied force does positive work, adding KE.
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What is gravitational potential energy near Earth in terms of height?
What is gravitational potential energy near Earth in terms of height?
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$GPE=mgh$. GPE depends on mass, gravity, and height.
$GPE=mgh$. GPE depends on mass, gravity, and height.
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When an object falls (ignore air resistance), what energy conversion explains the speed increase?
When an object falls (ignore air resistance), what energy conversion explains the speed increase?
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$GPE$ decreases and transfers to $KE$. Falling converts height energy to motion energy.
$GPE$ decreases and transfers to $KE$. Falling converts height energy to motion energy.
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When an object is lifted at constant speed, what energy transfer occurs?
When an object is lifted at constant speed, what energy transfer occurs?
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Work transfers energy to increase $GPE$. Lifting does work against gravity, storing GPE.
Work transfers energy to increase $GPE$. Lifting does work against gravity, storing GPE.
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What is elastic potential energy for an ideal spring compressed or stretched by $x$?
What is elastic potential energy for an ideal spring compressed or stretched by $x$?
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$E_{elastic}=\frac{1}{2}kx^2$. Elastic PE depends on spring constant and displacement squared.
$E_{elastic}=\frac{1}{2}kx^2$. Elastic PE depends on spring constant and displacement squared.
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When a stretched rubber band launches an object, which energy transfer explains the motion?
When a stretched rubber band launches an object, which energy transfer explains the motion?
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Elastic potential energy transfers to $KE$. Stored spring energy converts to motion energy.
Elastic potential energy transfers to $KE$. Stored spring energy converts to motion energy.
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Identify the energy transfer when brakes stop a bicycle wheel.
Identify the energy transfer when brakes stop a bicycle wheel.
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Kinetic energy transfers to thermal energy. Brake friction converts motion to heat.
Kinetic energy transfers to thermal energy. Brake friction converts motion to heat.
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A $2,kg$ cart speeds up from $3,m/s$ to $5,m/s$; what is $\Delta KE$?
A $2,kg$ cart speeds up from $3,m/s$ to $5,m/s$; what is $\Delta KE$?
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$16,J$. $KE_f = \frac{1}{2}(2)(25) = 25J$, $KE_i = \frac{1}{2}(2)(9) = 9J$, so $\Delta KE = 16J$.
$16,J$. $KE_f = \frac{1}{2}(2)(25) = 25J$, $KE_i = \frac{1}{2}(2)(9) = 9J$, so $\Delta KE = 16J$.
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If $W_{net}=30,J$ on an object, what is $\Delta KE$?
If $W_{net}=30,J$ on an object, what is $\Delta KE$?
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$30,J$. By work-energy theorem, $\Delta KE$ equals net work done.
$30,J$. By work-energy theorem, $\Delta KE$ equals net work done.
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A $10,N$ push acts over $4,m$ in the direction of motion; what work is done?
A $10,N$ push acts over $4,m$ in the direction of motion; what work is done?
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$40,J$. $W = Fd = (10N)(4m) = 40J$ when force is parallel to motion.
$40,J$. $W = Fd = (10N)(4m) = 40J$ when force is parallel to motion.
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Which statement best defines kinetic energy in terms of motion?
Which statement best defines kinetic energy in terms of motion?
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Kinetic energy is the energy an object has because it is moving. Motion itself is the defining characteristic of kinetic energy.
Kinetic energy is the energy an object has because it is moving. Motion itself is the defining characteristic of kinetic energy.
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What is the formula for kinetic energy of an object with mass $m$ and speed $v$?
What is the formula for kinetic energy of an object with mass $m$ and speed $v$?
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$KE = \frac{1}{2}mv^2$. Formula shows KE depends on mass and square of velocity.
$KE = \frac{1}{2}mv^2$. Formula shows KE depends on mass and square of velocity.
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What happens to kinetic energy when speed doubles and mass stays constant?
What happens to kinetic energy when speed doubles and mass stays constant?
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It becomes $4$ times larger. KE depends on $v^2$, so doubling $v$ gives $2^2 = 4$ times more energy.
It becomes $4$ times larger. KE depends on $v^2$, so doubling $v$ gives $2^2 = 4$ times more energy.
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What happens to kinetic energy when mass doubles and speed stays constant?
What happens to kinetic energy when mass doubles and speed stays constant?
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It becomes $2$ times larger. KE is directly proportional to mass when velocity is constant.
It becomes $2$ times larger. KE is directly proportional to mass when velocity is constant.
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What is the definition of energy transfer in a motion situation?
What is the definition of energy transfer in a motion situation?
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Energy transfer is energy moving from one object or system to another. Energy cannot be created or destroyed, only moved between objects.
Energy transfer is energy moving from one object or system to another. Energy cannot be created or destroyed, only moved between objects.
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What is the definition of work as energy transfer by a force?
What is the definition of work as energy transfer by a force?
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Work is energy transferred when a force causes displacement. Force must move an object to transfer energy as work.
Work is energy transferred when a force causes displacement. Force must move an object to transfer energy as work.
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State the formula for work when force and displacement are in the same direction.
State the formula for work when force and displacement are in the same direction.
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$W = Fd$. Work equals force times displacement when aligned.
$W = Fd$. Work equals force times displacement when aligned.
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If a force does positive work on an object, how does the object’s kinetic energy change?
If a force does positive work on an object, how does the object’s kinetic energy change?
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Kinetic energy increases. Positive work adds energy to the object's motion.
Kinetic energy increases. Positive work adds energy to the object's motion.
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