1 / 24

Forces

Forces. Newton’s Laws: Law of Inertia states that an object will not move until a force is exerted Law of constant acceleration- if a force keeps acting on the moving objects then it will accelerate Conservation of Movement- For every action there is an equal and opposite reaction.

brandylopez
Download Presentation

Forces

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Forces Newton’s Laws: Law of Inertia states that an object will not move until a force is exerted Law of constant acceleration- if a force keeps acting on the moving objects then it will accelerate Conservation of Movement- For every action there is an equal and opposite reaction

  2. What Is A Force? • A force is a push or a pull • You have to push or pull doors to open them • Which do you do when you jump up? • Your legs push off the ground • Which do you do when you climb a rope? • You pull yourself up

  3. What Units Are Forces Measured In? • The are measured in Newtons (N) • These units are named after Sir Isaac Newton • Weight is measured in Newtons • There are 10 N in every 1 Kg • If my mass is 80 Kg how much do I weigh? • 80 x 10 = 800 N

  4. What Can Forces Do? • They can change the speed of an object • They can change the direction an object is moving • They can change an objects shape • Which of these happens when you stamp on a coke can? • Change it’s shape • Which of these happens when you flick an elastic band? • You change it’s speed and it’s shape

  5. Measuring Forces • Forces are measured using Newton meters (sometimes called Force meters) • These have springs inside them • This means that they can break if too much weight is put on them

  6. Mass Or Weight • Mass is how much matter we are made of • Your mass is the same everywhere you go • Weight is a mass being pulled by gravity towards the Earth • You are weightless is space • You would be six times lighter on the moon • You would be 10 times heavier on Jupiter • In all of these places you would have the same mass

  7. Mass or Weight • What is the astronauts mass on Earth? • 120Kg • His mass on the moon? • 120 Kg • His weight on Earth? • 1,200 N • His weight on the moon? • 200 N • Why does he weigh less on the moon? • It is six times smaller than the Earth, it has less gravity

  8. Gravity • This is when objects are pulled towards large objects • What does the Earth’s gravity do to us? • It pulls us towards the Earth • Why does the Earth go around the Sun? • The Sun’s gravity keeps us in orbit • Which would have more gravity; the Earth or the Sun? • The Sun because it is much bigger • The escape velocity of a rocket leaving the Earth is 11.2 km/sec (40,000 km/hour)

  9. Galileo • Legend has it that Galileo took a canon ball and a wooden ball the same size to the top of this tower • He dropped them at the same time • Which hit the ground first? • They both hit the ground at the same time! Leaning Tower of Pisa

  10. Friction • This happens when two surfaces rub against each other • It creates heat • It slows things down • How do bike brakes stop a bike? • The brake pad presses against the wheel until friction slows it till it’s stopped. The tyre of the wheel then rubs against the ground slowing the bike down, until friction stops it

  11. Friction • Why is friction useful to: • Us when we are running? • Friction allows us to stop • The brakes in a car? • It allows the car to slow down or stop • Why is friction a nuisance if: • You fall on gravel? • You get burns or grazes • If you don’t oil a bike chain? • The chain will stop moving

  12. Reducing Friction • Engine parts and bike chains are oiled • This is called lubrication • This prevents wear and tear • It saves money because the engine does not have to work as hard

  13. Reducing Friction • Swimmers attempting long swims cover themselves in grease • Ball bearings can be used (e.g. in gear boxes)

  14. Upthrust • This is the force that pushes things up when they are in water • It is a weak force • Polystyrene is full of air holes, this means it is light and can be pushed to the surface of a swimming pool • Why do steel ships float? • They are hollow (full of air) and have a large surface area for upthrust to push up

  15. Thrust and Air Resistance • Thrust if a forward force • Air Resistance (drag) is when air particles slow things down • When would air resistance be a nuisance? • It slows down cars, aeroplanes, animals running etc. • When would it be useful? • Parachutes

  16. This Ferrari GG50 is streamlined to make it go faster

  17. Streamlining Reduces Drag This bottlenose dolphin is streamlined to reduce drag in water

  18. Force Diagrams • Arrows show the direction of the force • Their thickness illustrates the size of the force • These two forces are balanced, the book is not moving

  19. Force Diagrams • Name the force that slows the car down? • Friction (and drag) • What should happen to the car? • It will slow down 400N 500N

  20. Force Diagrams • What will happen to this truck? • It will stay still • What will happen to this truck? • It will move forward

  21. Gravity 1

  22. Gravity Upthrust They are equal 0

  23. Gravity 5

  24. Gravity Upthrust A is bigger than b 4

More Related