Forces | Year 8 Physics (Cambridge) PDF Download

Forces

Balanced and Unbalanced Forces

• Definition: Forces are balanced when the resultant force acting on an object is zero. This means that there is no overall change in the object's state of motion.
• Examples: A stationary object or an object moving at a constant speed without changing direction.
• Unbalanced Forces: Result in a change in motion—either starting, stopping, or changing speed or direction.
• Example: Pushing a car to make it move or applying brakes to stop it.

Turning Effect of a Force

• Definition: Also known as torque, it is the rotational effect of a force.
• Example: Turning a wrench to tighten a bolt—force applied at a distance from the pivot point creates torque.
• Principle: Larger force or longer lever arm increases the turning effect.

Pressure

Pressure on an Area

• Definition: Pressure is the force applied perpendicular to the surface of an object per unit area.
• Formula: 
• Example: Sitting on a chair—more pressure on a smaller area can be uncomfortable compared to spreading the weight over a larger area.

Pressure and Diffusion in Gases

• Diffusion: The movement of particles from an area of high concentration to an area of low concentration.
• Pressure's Role: Higher pressure can increase the rate of diffusion by forcing particles closer together, speeding up collisions and movement.
• Example: Inflating a balloon—increasing pressure inside forces air out when released, equalizing pressure with surroundings.