Effects of Force

8.2  Effects of Force  
  • Force can change shape, size and motion of the object

Effects of force

  1. Moving a stationary object
  2. Stopping a moving object
  3. Changing the speed of an object that is in motion
  4. Changing the direction of an object that is in motion
  5. Changing the shape and size of an object

Buoyant Force and Density

Buoyant force = Actual weight - Apparent weight
  • The denser the object, the lesser the buoyant force than the object. Thus, the object submerge
  • The less dense the object, the higher the buoyant force than the object. Thus, the object float


  • Lever is a bar that rotates on a fixed point
  • Lever has three parts

Effort - Force applied on the bar

Load - Object to be moved

Fulcrum - Fixed support point


Classification of levers

First class lever Second class lever Third class lever
Fulcrum is between load and effort Load is between fulcrum and effort Effort is between fulcrum and load

The Moment of Force

  • A force acting on an object can rotate the object at a fixed point. The turning effect produced is moment of force.
Moment of force = Force(N) x Perpendicular distance from the      pivot to the (m)


  • Pressure is defined as force per unit area (direction of force is perpendicular to the surface area)
  • S.I. unit for pressure is pascal (Pa)
Pressure = Force (N) / Surface area (\(\text{m}^2\))

Gas Pressure

  • The frequency of collision between the air molecules and the walls of the container will produce a force that pushes against the walls which is called air pressure

Factors that affect gas pressure

  1. Volume
  2. Temperature

Atmospheric Pressure

  • Atmospheric pressure is the pressure exerted by the atmosphere on the surface of the Earth and all objects on the Earth
Application of the concept of air pressure in daily life
  • Plunger
  • Magdeburg Hemisphere
  • Straw
  • Syphon
  • Syringe
  • Vaccum cleaner

Relationship between Altitude and Atmospheric Pressure

  • Atmospheric pressure decreases as altitude increases

Effects of Depth on Liquid Pressure

Examples of Effects of Depth on Liquid Pressure
  1. The walls of a dam are designed to be thicker at the base in order to withstand the high water pressure at the base of the dam
  2. A diver wears a special suit in order to withstand high water pressure