Understanding Forces: Weight, Friction, and Tension

• Forces are pushes or pulls that can affect an object's motion.
• Forces are vector quantities, meaning they have both magnitude and direction.
• Forces are measured in newtons (N).
• Forces can cause objects to: Start moving, Stop moving, Speed up, Slow down, Change direction, Change shape

Types of Forces

• Weight is the force of gravity acting on an object.
• Weight is measured in newtons (N)
• Weight is calculated using: weight = mass × gravitational field strength (W = mg)
• Mass is measured in kilograms (kg).
• Gravitational field strength (g) is measured in newtons per kilogram (N/kg) and varies depending on the celestial body. On Earth, g ≈ 9.8 N/kg.
• Friction is a force that opposes motion when two surfaces rub against each other.
• Friction results in energy transfer to the surroundings
• Air resistance (drag) is a type of friction that opposes the motion of objects through the air
• Tension is the force transmitted through a string, rope, cable, or wire when it is pulled tight by forces acting from opposite ends.
• Upthrust is the upward force exerted by a fluid (liquid or gas) on an object that is partially or fully immersed in it.

Balanced Forces

• Balanced forces result in no change in motion.
• If the forces on an object are balanced, the object will either remain stationary or continue to move at a constant velocity.
• Balanced forces: resultant force is zero

Unbalanced Forces

• Unbalanced forces result in a change in motion.
• If the forces on an object are unbalanced, the object will accelerate in the direction of the resultant force.
• Unbalanced forces: resultant force is not zero

Resultant Force

• The resultant force is the single force that is equivalent to all the individual forces acting on an object.
• If forces act in the same direction, they are added together.
• If forces act in opposite directions, one is subtracted from the other.
• Resultant force is calculated by vector addition of all forces acting on the body.

Work Done

• Work done is the energy transferred when a force causes an object to move.
• Work done is measured in joules (J).
• Work done is calculated using: work done = force × distance (W = Fd)
• Force is measured in newtons (N)
• Distance is measured in metres (m).
• 1 joule = 1 newton-metre

Extension and Compression

• Forces can cause objects to stretch (extension) or compress.
• Elastic deformation: the object returns to its original shape when the force is removed.
• Inelastic deformation: the object does not return to its original shape when the force is removed.
• The extension of a spring is directly proportional to the force applied, provided the limit of proportionality is not exceeded (Hooke's Law).
• Force is calculated using: force = spring constant × extension (F = ke).
• Spring constant (k) is measured in newtons per metre (N/m).
• Extension (e) is measured in metres (m).

Pressure in Fluids

• Pressure is the force exerted per unit area.
• Pressure is measured in pascals (Pa)
• Pressure is calculated using: pressure = force ÷ area (p = F/A)
• Force is measured in newtons (N).
• Area is measured in square metres (m²).
• 1 pascal = 1 newton per square metre.
• In liquids, pressure increases with depth and density of the liquid.
• Pressure is calculated using: pressure = height × density × gravitational field strength (p = hρg)
• Height/depth (h) is measured in metres (m).
• Density (ρ) is measured in kilograms per cubic metre (kg/m³).
• Gravitational field strength (g) is measured in newtons per kilogram (N/kg).

Moments

• A moment is the turning effect of a force around a pivot.
• Moment is measured in newton-metres (Nm).
• Moment is calculated using: moment = force × perpendicular distance from the pivot (M = Fd)
• Force is measured in newtons (N).
• Distance is measured in metres (m).
• In equilibrium, the total clockwise moment about a pivot is equal to the total anticlockwise moment about the same pivot.

Levers

• Levers are simple machines that make it easier to do work by increasing the distance over which a force is applied.
• Levers use a pivot to reduce the force needed to achieve the same moment.
• Examples of levers: seesaws, crowbars, scissors.

Gears

• Gears are toothed wheels that transmit rotational motion and forces.
• Gears can change the speed, direction, and torque of a rotational force.
• Larger gears rotate slower but have greater torque.
• Smaller gears rotate faster but have less torque.

Explore the fundamental concepts of forces, including weight, friction, and tension. Learn how forces affect motion and are measured in newtons. Understand the relationship between mass, weight, and gravitational field strength, as well as the effects of friction and air resistance.