YR 8 Topic 2. Forces Select the online test

Key Concepts

Vocab

More Vocab


A force is a push or a pull. Simple machines use less force or change the direction of a force.
Levers are force multipliers or speed multipliers
Mechanical advantage is the load divided by the effort. (or the distance of the effort from the fulcrum divided y the distance of the load from the fulcrum)
A wheel is a bent lever that rotates around the axle (fulcrum) Gears are a special kind of wheel
Pulleys can be used to reduce the effort required to lift a load. We can calculate work and Mechanical advantage
Simple machines
Ramp
Lever
Inclined plane
Screw
Force
Effort
Load
Work = force X distance
Mechanical advantage = Load / Effort
Pulley
wheel
torque
gear
Lever
fulcrum
teeth

Concepts

Suggested activity

Extension activity


8.1 Simple Machines
A force is a push or a pull. Simple machines use less force or change the direction of a force.
Calculate work and mechanical advantage.
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  1. Ques 17 to 27 Science at work p 244
  2. try this simple machines song
http://www.youtube.com/watch?v=l1Fhs8pXGxM&feature=related

8.2 Levers
Levers are force multipliers (Class 1 and 2)
Correctly use terms fulcrum, effort, load
Levers are speed multipliers (Class 3)
Calculate Mechanical advantage and work done
  • Use a variety of levers and draw them to show the effort and load and fulcrum
  • View this site and make some notes http://edhelper.com/SimpleMachines.htm
  • Draw and label examples of a Class 1 lever, a Class 2 lever and a Class 3 lever.
  • p249 Q 1 to 10
  • p250 Q 17 to 19
  • do at least 2 of the following pracs
  • Prac 1 -p251
  • Prac 2 - p252
  • Prac 3 - p253
  • Hmwk - 8.2
  1. Surfing - p257
  2. Constructing p 257
  3. Watch this tv add using levers

8.3 Wheels axles and gears
Wheels and axles
Gears
Calculate Mechanical advantage and work done
  • Construct a table to compare Wheels as force multipliers and Speed multipliers include examples of each (p258 to 259)
  • Draw and label a gear system - see p260
  • Play with the Lego gears - new equip available, mouse trap racer, or cotton reel racer
  • Write a paragraph on how Gears can be used as a force multiplier or a speed multiplier
  • Questions p 261- 1 to 10 and Q17 and 18
  • Hmwk 8.4
• Use the STELR Windmills to explore gearing and power output
• Hmwk 8.5

8.4. Pulleys
Single pulleys change direction of a force
Multiple pulleys use a small effort to lift a large load
Calculate Mechanical advantage and work done
  • Draw examples of single pulley systems and label the effort and load
  • Draw examples of a multiple pulley system and label the effort and the load
  • Prac 1 p 268
  • Prac 2 p 269
  • Use the formula Work = effort force X the distance moved to calculate the work done in Prac 2 - how does this compare to the results gained fro the prac.
  • p267 Ques 1 to 10 and Q 14 and 16
  • Hmwk 8.6 and 8.7
More on Prac 2 - What are Newtons and why are they used in this topic?
Prac 3 - p270
Prac 4 - p271

Putting it all together
Use the things you have learnt - This is an assessment task


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Online test

Online test

Instructions
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  1. put your class in front of your first name (in the first field or type box) Eg 8H Sarah
  2. put your last name in the second field Eg Smith
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Yr 8 Using Forces