Force- final.ppt
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Here are the steps to re-arrange the surfaces by slipperiness: 1. Ice 2. Wet Mud 3. Wet Grass 4. Thick Carpet 5. Wet concrete 6. Dry concrete 2. a. An ice skater performing a routine wants as little friction as possible. b. A driver driving a car on a wet road wants as much friction as possible. c. A mountain biker riding down a steep muddy hill wants as little friction as possible.
Force- final.ppt
- 1. Forces
- 2. Starter What do you think a force is?
- 3. What is a force? A force is a push (or a pull)
- 4. What is a force? A force can change the shape of an object
- 5. What is a force? A force may also change the speed and direction of an object
- 6. Lesson Objectives • To explain what a force is and know the different types of forces • Be able to measure force using a force meter
- 7. Contact forces Many forces need contact to affect an object
- 8. Non-contact forces Some forces can affect an object from a distance
- 9. Friction Tension (Pull) Air Resistance Static Electricity Applied Force (Push) Magnetic Force Gravity Spring Force (Twist)
- 10. Different types of forces Non- Contact Forces Gravity Magnetic Force Electrical Force Contact Forces Friction Tension (Pull) Air Resistance Applied Force (Push) Spring Force (Twist) http://www.physicsclassroom.com/class/newtlaws/u2l2b.cfm
- 11. Measuring force • We can measure a force with a forcemeter Forces are measured in units called NEWTONS.
- 12. Measuring forces The force of gravity pulling on an apple is about 1 N 1 N
- 13. Measuring forces The force needed to pull a truck is about 3000 N 3000 N
- 15. Lesson Objectives • Explain why some objects float and some objects sink • Investigate if materials will float based on it’s density • Measure the density of substances
- 16. Upthrust and Gravity Gravity is the pull of the earth on something Upthrust is the push upwards of a liquid on something.
- 17. Objects weigh less in water because the water pushes the object upwards. This force is called ______________ When __________ and ___________ are equal, the object will FLOAT. UPTHRUST UPTHRUST GRAVITY
- 18. When gravity is bigger than upthrust, the object will _____ If upthrust is bigger than gravity, the object will move _________, out of the water. SINK UPWARDS
- 21. Investigate Archimedes principle • Make a table like this for 5 objects Object Volume cm3 Mass g Density g/cm3 Float or sink?
- 22. Method 1. Record the weight of the object using scales 2. Record it’s volume using the eureka can 3. Work out the density 4. Does it float or sink?
- 23. Conclusion When density is greater than 1 it sinks, if it’s less, it floats
- 24. density • It is the ____________________of an object • It is the density of an object that will determine whether or not an object will _____________ or sink in _________________ • If an object is ____________ dense than water it will float • If an object is ______________ dense than water it will sink water, less, heaviness, float, more
- 25. upthrust or buoyancy thrust air resistance friction weight Label the forces acting on the ferry as it sails to France.
- 26. Upthrust in action This boat has gravity pushing it down, and the upthrust of the water pushing up. Because the forces are balanced, the ship floats. Upthrust Gravity
- 27. If the forces on an object are balanced: •an object that is not moving stays still •an object that is moving continues to move at the same speed and in the same direction If the forces on an object are unbalanced: •An object that its not moving starts to move •An object that is already moving changes speed or direction Balanced & unbalanced forces What is the resultant force?
- 28. We can show the forces acting on an object using a force diagram. In a force diagram, each force is shown as a force arrow. Forces are measured in: Newtons (N) An arrow shows: •The size of the force (the longer the arrow, the bigger the force) •The direction in which the force acts.
- 30. Copy & complete • A force can be a push or a pull. It is measured in ......................... • If the forces acting on an object are balanced then it is ................... or travels at a ..................... speed • If the forces acting on an object are unbalanced, then it is either changing .......................... or ...................................... • Mark diagrams with arrows to show forces. • Write the name of the force • Label diagrams balanced or unbalanced • If the forces are unbalanced, show the biggest force with the biggest arrow Car braking Missile just launched
- 31. 10 N 10 N If you link two forcemeters and pull equally hard from both ends, the forces recorded on both will be the same. balanced forces When forces are balanced The forces acting on the central hooks cancel each other out – they are equal in magnitude and opposite in direction. Because the forces are balanced the hooks do not move.
- 32. 11 N 10 N What happens if the pull on one end is greater than the pull on the other end? unbalanced forces movement When forces are unbalanced The forces acting on the hooks are no longer balanced. Both hooks will start to move to the left – their speed will change. This is called acceleration. Unbalanced forces lead to a change in speed or direction.
- 33. In which direction will these stationary objects move?
- 34. Weight = 200N Air resistance = 600N
- 35. Friction
- 36. Starter: What is friction? • Friction is a force that is always in the opposite direction to the moving object • It happens when two surfaces rub together • Whenever any two objects rub together there is a force that makes them not glide smoothly • Friction is also able to take the energy of moving objects and turn it into heat
- 37. Design and carry out an experiment to test out friction Learning Objective:
- 38. 2.Why do you think that? OBJECTS WITH SMOOTHER SURFACES TRAVEL FASTER _________________________ _________________________ ________________ 1.What do you think? ____________ ____________ ____________ ____________ ____________ ____________ ____________ ____________ ____________ ____________ ________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ 4.Do you still think this? 5.How could you improve? YE S No 3.How could you prove this? (Hypothe sis) (Evaluatio n) (Predictio n) (Metho d)
- 39. • Measure 1 metre on a plank of wood • Slide a block of material down a plank of wood • Time how long it takes to go down • Repeat using a different type of material
- 40. 1.Re-arrange these surfaces into order of slipperiness from least slippery to most slippery. Thick Carpet Wet concrete Dry concrete Ice Wet Grass Wet Mud 2.Do the following people want to make as much friction as possible or as little friction as possible? a. An ice skater performing a routine b. A driver, driving a car on a wet road c. A mountain biker riding down a steep muddy hill