Science

• Force


  A push or pull. Stretch and squeeze can also be used to denote force.
• Types of Forces


  • Contact forces
  • Non-Contact forces
• Contact forces


  • Contact forces are the forces that occur due to the contact between two different objects
  • Examples: Spring force, air resistance force, tension force and frictional force
• Non-Contact forces


  • A non-contact force is a force applied to an object by another body that is not in direct contact with it
  • Non-contact forces come into play when objects do not have physical contact between them or when a force is applied without any interaction
  • Example: Gravitational Force
• Spring Force


  The force required or exerted to compress or stretch a spring upon any object that is attached to it<|>Spring force has a restoring force that can retract the string back to its original spring<|>Spring force can be found in in elastic materials<|>Example: Rubber band, bungee cord, trampoline and spring balance
• Air Resistance Force


  The force exerted by a gas acting upon a body on the opposite direction<|>Examples are the forces experienced by a skydiver or a downhill skier
• Tension Force


  This type of force is experienced by a rope or a string which holds an object<|>The tension force is always a pull not a push<|>The tension force is same throughout the cable<|>Example: a ball hanging with the help of a string / pulling a rope / Car Towing / Pulling a bucket of water from well
• Frictional Force


  Frictional force refers to the force generated by two surfaces that contact and slide against each other<|>Example: A box is slid on a table<|>Different surfaces produce different amount of friction
• Gravitational Force


  Gravitational force is the force of attraction on a body by earth<|>The weight of an object is the force of gravity acting on it<|>The force of gravity acting on an object on the moon is weaker than on Earth<|>Gravity enables all the things around us to stay in place
• Weight


  The weight of an object is the force of gravity acting on it
• Mass and weight are not the same
• Mass


  The measure of the amount of matter in a body
• Weight


  The force of gravity acting on an object
• Effects of Force


  • Can change the speed of an object
  • Can change the direction of a moving object
  • Can change the size or shape of an object
• Effects of Force


  • Increase the speed by pushing harder on the pedals of bicycle
  • Pressing the hand brake of a bicycle for slowing down
  • When a football player kicks a moving ball
  • The wind allows sail boat to change direction
  • When air is blown into the balloon cause the balloon to expand
  • Pressing a plasticine
  • Squeezing a sponge
• Work Done


  Work is done when an object moves while a force is being exerted on it<|>The conditions for work done are: Force acting on an object, The object moves, The movement of the object is in the direction of the force
• Work Done


  Work done = Force x Distance moved in the direction of the force<|>S.I unit: joule (J)
• Work Done (Example 1)

  • Insyirah carries a 80N school bag up a flight of stairs, 3m high. Calculate the amount of work done against gravity to carry the school bag upstairs.
• Work Done (Example 2)


  • Zahra lifts a 50N weight to a height of 1 m from the floor. Calculate the amount of work done
• Work Done (Example 3)

  • Rais uses 100 N of force to push the lawnmower. He pushes it for a total of 200 m as he cuts the grass in his grandmother's yard. How much work does he do?
• Work Done (Example 4)

  • After Rais mows his grandmother's lawn, he volunteers to mow a neighbor's lawn as well. If he pushes the mower using 100 N of force and moves it over a total of 234 m, how much does he do mowing the neighbor's lawn?
• Pressure


  Pressure is defined as the amount of force acting per unit area<|>S.I Unit: Pascal (Pa) or Newton per square metre (N/m²)<|>Pressure depends on the amount of force used and the area of contact
• High pressure


  A force acting on a small area of contact
• Low pressure


  A force acting on a large / wide area of contact
• Pressure Example


  • An elephant and a lady stand on a floor. The lady's shoes have sharp heels. The weight of the elephant is 40 000 N and the area of its foot is 1000 cm2. For the lady, her weight is 400 N and the area of her shoe heel is 1cm2. Which will damage the floor more?
• Applications of Pressure


  • The studs of the football shoe decrease the area of contact with the ground. This will increase the pressure causing the studs to sink into the ground and hence preventing the player from slipping.
• Applications of Pressure


  • Bulldozer is heavy and will not sink into the mud or sand. This is because bulldozer uses steel track that have a large surface area to reduce the pressure on the ground.