1. read each slide carefully. record notes on notebook paper. give your notes a title: “work...
TRANSCRIPT
1
Read each slide carefully. Record notes on notebook paper. Give your notes a title: “Work Notes” Write the title of each page in which you
will record notes and underline it. When you see this indicates
that you should write the information beside it.
Underline and highlight new vocabulary words.
2
Work is done when a force causes an object to move a distance in the direction of the applied force.• Work=Force x Distance• If the object doesn’t move by the force, no
work is done
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Girl pushes the box work is done!
She’s working really hard, but the car is not moving. No work is done here.
What about this guy? Is he doing work as he carries his laundry to his room?
1. A scientist delivers a speech to an audience of his peers.
2. A body builder lifts 350 pounds above his head.
3. A mother carries her baby from room to room.
4. A father pushes a baby in a carriage.
5. A woman carries a 20 kg grocery bag to her car?
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A scientist delivers a speech to an audience of his peers. NoNo
A body builder lifts 350 pounds above his head. YesYes
A mother carries her baby from room to room. NoNo
A father pushes a baby in a carriage. YesYes
A woman carries a 20 km grocery bag to her car? NoNo
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No movement (even if there is force)=NO work is done
No work is done if you are just carrying an object around
If an object is moving but no force is applied NO work is done (ball flying through the air)
Work is only done when a force causes an object to move a distance.
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Work = Force x Distance The unit of force is newtons (N) The unit of distance is meters (m) The unit of work is newton-meters One newton-meter is equal to one
joule So, the unit of work is a joule (J)
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Work = Force x Distance
Calculate: If a man pushes a lawn mower 10 meters with a force of 20 N, how much work has he done?
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Work = Force x Distance
Calculate: If a man pushes a lawn mower 10 meters with a force of 20 N, how much work has he done? 200 joules200 joules(W = 20N x 10m)(W = 20N x 10m)
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What if you are given work and asked to find force or distance?
Cover up the variable you are trying to find and then solve what’s left.
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F D
W
You did 10J of work lifting a 10-newton book, how high did you lift the book?
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F D
W
More force= more workLess force=less work
More distance(force same)=more work
Work=Force x Distance
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Vs.
A ramp decreases the force required to lift an object but increases the distance over which the force is applied.
The work is easier but the AMOUNTAMOUNT of work done does not change (assuming there’s no friction)
The amount of work done with or without a ramp is the same.
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Steeper slope=more force but less distance so….
The AMOUNTAMOUNT of work is the samesame assuming no friction.
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Other simple machines such as pulley’s, levers, and wheel and axles affect work in the same way. They decrease force and increase distance making the work easier but the amount of work done does not change.