ch 6 test: controlling heat transfer please remove hats and hoods
TRANSCRIPT
Ch 6 Test: Controlling Heat Transfer
Please remove hats and hoods
Ch 7 Simple Machines
Science 14 and 10-4 with Mrs M
Please remove your hats
7.1 Many types of Energy
• We have already talked about thermal energy or heat
• Kinetic energy = energy of motion (recall temperature is the average of kinetic energy)
• What about the energy used in machines?
Many types of energy
• Energy is the ability to do work
Work = Force x distance
• W = F x d• Work is a form of energy measured in Newton
meter (Nm) or Joules (J)• Work is defined as a force applied over a
distance
Which requires more effort or force, a short/steep or a long/gradual ramp?
W = F x d
• A force of 20 N is required to lift a box. The box is lifted from the floor to a shelf that is 2m high. What is the amount of work done?
• W = F x d• W = 20 x 2• W = 40 Nm
W = F x d
• Pushing a wheelbarrow takes 8000 Nm of work. How much force was needed to move it 25 m?
Simple Machines
• Simple machines have one movement• The movement of an inclined plane/ramp is a
slide.• A ramp is an old simple machine
Work requires a FORCE input over a DISTANCE
No Work
Work being done by pedaling force uphill
Pushing against a wall is NOT work… because it’s not moving!
Quick Quiz #5
• Open book• Individual
Levers
• Lever: a rigid bar resting on a pivot, used to help move a heavy load/weight– Fulcrum= pivot point– Load= weight to be moved– Effort= force applied
LeversFulcrum in middle 1st class
Load/Weight in the middle 2nd classEffort/Force in the middle 3rd class
1st classEffort, Fulcrum, Load
1st class levers
1st classFulcrum in the middle
2nd Class LeverLoad or Weight in the middle
2nd class levers
2nd classLoad or weight in the middle
3rd Class LeversEffort or Force in the middle
3rd class levers
3rd class leverEffort in the middle
FLE 123
Why should a heavier person sit closer to the fulcrum on a teeter totter?
Center of massGirl’s Work = Boy’s Work
Girl’s Force x girl’s distance = Boy’s Force x boy’s distanceWeight(girl)x d = Weight(boy)x d
The little girl’s weight is 133 N and sits 0.5m from the middle of the teeter totter. How far
away does the boy sit if he weighs 265 N?
Weight(girl)x d = Weight(boy)x d133 x 0.5 = 265 x d
(133x0.5)/265 = d