Force and Motion

• Force is a pull or a push upon an object.
• Gravitational Force is a force that points towards the center of the Earth and causes objects thrown upwards to fall back to Earth.
• Weight is defined as the gravitational force acting on an object and is dependent on its mass.
• Normal Force is the force produced when an object is in contact with a surface.
• Elastic Force exists when a material is stretched or compressed.
• Buoyant force is the thrust force acting on an object that is floating on the surface of a fluid.
• Frictional force is the force that resists movement between two surfaces in contact with each other.
• Characteristics of Force include magnitude, direction, and point of application.
• The unit of force is the newton (N), where 1 kg is equal to 10 N.
• Newton's Third Law states that for every action force, there is a reaction force of the same magnitude but in the opposite direction.
• Types of Forces include:

  • gravitational force
  • weight
  • normal force
  • elastic force
  • buoyant force
  • frictional force.
• Force cannot be seen, but its effects can be felt.
• When a force acts on an object, it can change the shape, size, and motion of the object.
• Five effects of force:

  • Moving a stationary object
  • Stopping a moving object
  • Changing the speed of an object that is in motion
  • Changing the direction of a moving object
  • Changing the shape and size of an object
• An object will float if the buoyant force acting on it is enough to support its weight.
• Buoyant force = weight of object
• Example 1: The rubber duck - Weight = 10 N, Buoyant force = 10 N, It will float.
• Example 2: Stone - Weight = 10 N, Buoyant force = 5 N, It will submerge.
• Buoyant force = Actual weight - Apparent weight
• Actual weight = weight of an object in the air
• Apparent weight = weight of an object immersed in fluid
• Density and Buoyant Effect: Object less dense than liquid = Buoyant force is more than weight of the object, The object will float.
• Density and Buoyant Effect: Object more dense than liquid = Buoyant force is less than weight of the object, The object will submerge to the bottom of the liquid.
• A lever is a bar that rotates on a fixed point and has three parts: load (L), effort (E), and fulcrum (F).
• A lever allows us to do work easily, such as opening a can lid with a spoon or opening a bottle cap with a bottle opener.
• A lever allows us to use minimal force to do work, such as lifting a heavy load or removing a nail.
• Levers are classified into three types: first class, second class, and third class, depending on the position of the effort, fulcrum, and load.
• In a first-class lever, the fulcrum is between the load and effort.
• In a second-class lever, the load is between the fulcrum and effort.
• In a third-class lever, the effort is between the load and fulcrum.
• The moment of force is the turning effect produced when a force acts on an object at a fixed point (fulcrum).
• The moment of force is calculated by multiplying the force applied (N) by the perpendicular distance from the fulcrum to the force (m).
• The unit for moment of force is Nm (Newton meter).
• The moment of force will increase if the magnitude of force increases or if the perpendicular distance from the pivot to the effort increases.
• The principle of moments of lever states that the load multiplied by the distance of the load from the fulcrum is equal to the effort multiplied by the distance of the effort from the fulcrum.
• Load (N) x Distance of load to fulcrum (m)= Effort (N) x Distance of effort to fulcrum (m)
• Easier way to move something effected by frictional force: use rollers or wheels.