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1 Work in Science. 2 What is work? In science, the word work has a different meaning than you may be familiar with. In science, the word work has a different.

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Presentation on theme: "1 Work in Science. 2 What is work? In science, the word work has a different meaning than you may be familiar with. In science, the word work has a different."— Presentation transcript:

1 1 Work in Science

2 2 What is work? In science, the word work has a different meaning than you may be familiar with. In science, the word work has a different meaning than you may be familiar with. The scientific definition of work is: using a force to move an object a distance (when both the force and the motion of the object are in the same direction.) The scientific definition of work is: using a force to move an object a distance (when both the force and the motion of the object are in the same direction.)

3 3 Work or Not? According to the scientific definition, what is work and what is not? According to the scientific definition, what is work and what is not? a teacher lecturing to her class a teacher lecturing to her class a mouse pushing a piece of cheese with its nose across the floor a mouse pushing a piece of cheese with its nose across the floor

4 4 Work or Not? According to the scientific definition, what is work and what is not? According to the scientific definition, what is work and what is not? a teacher lecturing to her class a teacher lecturing to her class a mouse pushing a piece of cheese with its nose across the floor a mouse pushing a piece of cheese with its nose across the floor

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6 6 Whats work? A scientist delivers a speech to an audience of his peers. A scientist delivers a speech to an audience of his peers. A body builder lifts 350 pounds above his head. A body builder lifts 350 pounds above his head. A mother carries her baby from room to room. A mother carries her baby from room to room. A father pushes a baby in a carriage. A father pushes a baby in a carriage. A woman carries a 20 kg grocery bag to her car? A woman carries a 20 kg grocery bag to her car?

7 7 Whats work? A scientist delivers a speech to an audience of his peers. No A scientist delivers a speech to an audience of his peers. No A body builder lifts 350 pounds above his head. Yes A body builder lifts 350 pounds above his head. Yes A mother carries her baby from room to room. No A mother carries her baby from room to room. No A father pushes a baby in a carriage. Yes A father pushes a baby in a carriage. Yes A woman carries a 20 km grocery bag to her car? No A woman carries a 20 km grocery bag to her car? No

8 8 Formula for work Work = Force x Distance The unit of force is newtons The unit of force is newtons The unit of distance is meters The unit of distance is meters The unit of work is newton-meters The unit of work is newton-meters One newton-meter is equal to one joule One newton-meter is equal to one joule So, the unit of work is a joule So, the unit of work is a joule

9 9 W=FD Work = Force x Distance Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done?

10 10 W=FD Work = Force x Distance Calculate: If a man pushes a concrete block 10 meters with a force of 20 N, how much work has he done? 200 joules (W = 20N x 10m)

11 Work Work happens when a force moves an object over a distance. Work happens when a force moves an object over a distance. If the object does not move, NO work is done! If the object does not move, NO work is done! (Scientifically speaking) (Scientifically speaking)

12 Work Stand and hold your arms out in front of you at waist level, palms up. Stand and hold your arms out in front of you at waist level, palms up. Have your partner stack two books on your hands, one on each hand. Have your partner stack two books on your hands, one on each hand. Lift the books to about shoulder level, then lower them. Lift the books to about shoulder level, then lower them. Now try raising them overhead Now try raising them overhead

13 Work When your hands are overhead, are you working harder than when you raised them to shoulder level? When your hands are overhead, are you working harder than when you raised them to shoulder level? Describe your observations to your partner. Describe your observations to your partner.

14 Work Have your partner put two more books on each of your hands, so youre holding four books. Try to raise them to shoulder level. Have your partner put two more books on each of your hands, so youre holding four books. Try to raise them to shoulder level. Are you pushing harder (using more force) than when you were holding only two books? Are you pushing harder (using more force) than when you were holding only two books? Describe your observations to your partner. Describe your observations to your partner.

15 Work Hold the four books at shoulder level until your arms get tired. Are you exerting force? Hold the four books at shoulder level until your arms get tired. Are you exerting force? Do you think you are doing work in these situations? What is the work being done on? Do you think you are doing work in these situations? What is the work being done on? Describe your observations to your partner. Describe your observations to your partner.

16 Work You have 5 objects on your table. You have 5 objects on your table. Use the spring scale and a meter stick to find the force needed to move each object one meter. Use the spring scale and a meter stick to find the force needed to move each object one meter.


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