Basic Forces year 10 Physics powerpoint ml
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Forces act on objects in different ways: 1. Forces are pushes or pulls that can cause an object to start or stop moving in a certain direction. 2. If the forces on an object are balanced, the object will remain at rest or maintain a constant speed and direction of motion. 3. If forces are unbalanced, the object will accelerate in the direction of the greater net force.
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Basic Forces year 10 Physics powerpoint ml
- 1. What are forces? Forces act on you all the time: They are defined as the push or pull or twist on an object. Look at the following pictures and try to work out where the forces are and in which direction forces they are acting.
- 2. 1. 2. 3. 4. 5. 6.
- 3. The direction of the force is indicated by an arrow The size of the arrow indicates the size of the force a small arrow is less force A longer larger arrow is a greater force
- 4. When all the forces equal each other there is no change in movement and the object remains stationary or balanced
- 9. A constant forward motion indicates a balanced force. If the cyclist started to pedal harder what would happen?
- 10. What is happening here?
- 11. Movement Movement results in one force being bigger than another force. We call this an unbalanced force The object will move in the direction of the greater force.
- 14. Measuring forces A spring stretches when a pulling force acts on it It compresses when a pushing force acts on it. The bigger the force the more it stretches or compresses.
- 15. Measuring forces A spring can be used to measure force by the needle changing when the length of the spring changes. A spring balance measures pull Bathroom scales measure push
- 16. Weight and mass Weight is not the same as Mass Mass is the amount of matter an object contains and measured in Kg Weightis the force of the gravitational pull on the mass measured in Newtons Weight = mass x gravity ( approx 10) Yr 7 student mass = 40 Kg Gravity = 10N Weight of student is ??
- 17. Approximate sizes of some forces Force to lift and apple 1N Force to lift 1Kg bag of sugar 10 N Force you exert by sitting on someone 500N Force to launch a space rocket 33 000 000N Force can also be used in a horizontal direction eg. Pulling a door open
- 19. Gravity Gravity is a pulling force between things that have mass. The greater the mass of the objects the greater the force ie Earth has a larger gravitational pull than the moon which is smaller. The further the distance from the force the weaker it becomes
- 20. Measuring force The unit to measure force is the Newton named after the famous scientist Sir Isaac Newton a professor of mathematics and known for his theory of gravitational forces
- 21. Planets in orbit due to gravitational attraction
- 24. Falling objects Things fall because of gravity. The objects falls through air particles thus creating an air resistance. Air resistance opposes gravity and slows down the falling object The greater the surface area the greater the air resistance. Air resistance is dependent on the size shape and speed of the falling object See video clip
- 25. Terminal velocity As a falling objects speed increases so does the air resistance. Eventually the air resistance acting in the object is equal to its weight force The forces are balanced and the object is falling at a constant speed or its terminal velocity
- 26. Video clip
- 27. Gravity is considered a NON CONTACT force because it is not touching the object to have an effect on it. Other non contact forces are magnetic forces and electrostatic forces.
- 28. The strength of the gravitational pull is always the same 10N but the larger the mass of an object the larger the weight force ie Wt = mass X gravity . The greater the mass the The more force will be required to pull The more force will be required to push Think of an other examples to illustrate this concept.
- 30. Friction: A contact force unit 7:2
- 31. Friction exists whenever 2 surfaces are in contact; the force that makes most moving objects stop is FRICTION Friction provides grip needed by cars, bikes and your shoes to get moving. Think about running on a smooth or slippery surface vs a rough surface. Friction is needed to change direction and slow down. Friction causes heat: rub your hands together quckley. Friction can cause problems in machinery when the moving parts overheat
- 32. What affects friction? How rough the surfaces are: How hard the surfaces are pushed together: Due to how heavy the object is
- 33. Reducing Friction Rolling surfaces Lubricants Streamlined smooth Reducing area in contact with each other.
- 34. Inertia The tendency to resist any form of change in motion.
- 35. Newtons first law of motion An object will remain at rest unless acted on by a force. An object that is moving will continue to move at the same speed and in the same direction unless an unbalanced force acts on it
- 36. Inertia of the coin
- 37. The resistance of an object to change its state of motion If the car comes to a sudden stop the passengers keep moving forward until another force stops them ie windscreen, steering wheel of hopefully seat belt
- 38. A moving object will stay in that line of motion unless acted on by a force
- 39. Newtons second law of motion states An object will accelerate in the direction of an unbalanced force acting upon it. The size of the acceleration depends upon the mass of the object and the size of the force acting. F= m x a F m a
- 40. Same mass
- 41. Same force different mass = less acceleration for the larger mass
- 42. More acceleration more force applied to the ball
- 43. Newtons third law of motion For every action there is an equal and opposite reaction
- 46. Which Law and why?