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Work & Machines

Science, Grade 7

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increases force increases force decreases force force force motion motion decreases distance decreases distance increases distance Work is the exertion of force on an object that causes the object to move in the same direction in which the force is applied. If the object does not move as a result of the force applied, no work is done. How Much Work? Work = Force x Distance Newton (N) is the unit of measure for force, and meter (m) is the basic unit for distance. Work is expressed in (N • m) or the joule (J). Calculating Power Power is the rate at which work is done or the rate at which energy is transferred. To determine the amount of power (P), you divide the amount of work (W) done by the amount of time (t) it takes to do the work. Calculating Work To determine the amount of work, you multiply force times distance. The unit of measure for power is expressed in joules per second (J/s) also known as the Watt (W). Work (W) Time (t) Machines 1. A nutcracker increases the force but decreases the distance over which the force is applied. 2. A hammer decreases the force but increases the distance. 4. A simple pulley changes the direction of the input force, but the amount of input and output force remain the same. 3. A screwdriver used as a lever, increases the force and decreases the distance. lever inclined plane compound machine pulley gears wheel & axle wheel & axle Types of Machines changes direction of force - output remains the same Work is being done. No work is done. 1. 2. 3. 4. increases force increases force decreases force decreases distance decreases distance increases distance Machines Simple machines are devices designed to make work easier by changing the amount of force you exert, the direction of the force or the distance over which you exert the force. 1. A nutcracker increases the force but decreases the distance over which the force is applied. 2. A hammer decreases the force but increases the distance. 3. A simple pulley changes the direction of the input force, but the amount of input and output force remain the same. 4. A screwdriver used as a lever, increases the force and decreases the distance. changes direction of force - output remains the same 1. 2. 3. 4. 120 N 1 m 2 m Work = 120 N x 1 m = 120 N•m Work = 120 N x 2 m = 240 N•m Increasing the distance the weights are lifted also increases the amount of work done. Meaning of Work Power (P) = Simple machines are devices designed to make work easier by changing the amount of force you exert, the direction of the force or the distance over which you exert the force. © Copyright NewPath Learning. All Rights Reserved. 94-4801 www.newpathlearning.com Work & Machines

Work (W) Time (t) Power (P) = force motion Meaning of Work What is work? _________________________ _____________________________________________________ _____________________________________________________ How Much Work? Work = __________ x __________ ________________ is the unit of measure for force, and ________________ is the basic unit for distance. Work is expressed in ________________ or the ________________ . Calculating Power What is power? _______________________________ _____________________________________________ To determine the amount of power (P), you divide the amount of ________________ done by the amount of ________________ takes to do the work. Calculating Work To determine the amount of work, you multiply ________________ times ________________ . The unit of measure for power is expressed in ________________ also known as the ________________. Machines What are simple machines? _________________________________ _________________________________________________________ 1. A nutcracker ________________ the ________________ but ________________ the ________________ over which the force is applied. 2. A hammer ________________ the ________________ but ________________ the ________________ . 3. A screwdriver used as a ________________ , ________________ the ________________ and ________________ the ________________ . 4. A simple pulley ________________ the ________________ of the ________________ ________________ , but the amount of ________________ and ________________ ________________ remain the ________________ . Types of Machines Work is being done. 1. 2. 3. 4. 120 N 1 m 2 m Increasing the distance the weights are lifted also increases the amount of work done. Key Vocabulary Terms • force • power • joule (j) • simple machine • meter (m) • Watt (w) • Newton (N) • work © Copyright NewPath Learning. All Rights Reserved. 94-4801 www.newpathlearning.com Work & Mach ines \|xiBAHBDy01808nzW

Work & Machines

Science, Grade 7

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