91Ó°ÊÓ

Gravitational force is a fundamental concept in physics. It is the force that attracts any two objects with mass towards each other. This force is what makes apples fall from trees and keeps planets orbiting the sun. For any object near the surface of the Earth, the gravitational acceleration is usually taken as \(g = 9.8 \, \text{ms}^{-2}\).
The formula to calculate this force acting on an object is: - \(F_g = m \cdot g\) - where \(F_g\) is the gravitational force, \(m\) is the mass of the object, and \(g\) is the gravitational acceleration.
In the exercise, the gravitational force on a 0.05 kg object is calculated as \(0.49 \, \text{N}\). This force causes the object to accelerate downwards.

Net force is the overall force acting on an object when all individual forces are considered. According to Newton's Second Law of Motion, the net force \(F_{net}\) is related to mass \(m\) and net acceleration \(a_{net}\) by the equation:- \(F_{net} = m \cdot a_{net}\)Understanding net force is critical because it tells us how the motion of an object will change.
A net force causes a change in the object's velocity, leading to acceleration, deceleration, or a change in direction.
In our example, the net force is less than the gravitational force because air resistance also acts on the falling object. This results in a net force of \(0.47 \, \text{N}\).

When an object moves through the air, it experiences a force opposing its motion. This force is known as air resistance or drag force. Air resistance acts in the opposite direction to the motion of the object and increases with speed.
For falling objects, air resistance reduces the net acceleration below gravitational acceleration.
Mathematically, air resistance \(F_{air}\) can be determined by:- \(F_{air} = F_g - F_{net}\) - where \(F_g\) is the gravitational force and \(F_{net}\) is the net force.
In the exercise, air resistance was calculated to be \(0.02 \, \text{N}\), which is the difference between gravitational force and the net force.

Acceleration is the rate at which an object's velocity changes with time. It can be influenced by forces such as gravity and air resistance. In physics, acceleration is not only about changing speed, but also about changes in direction.
The key to understanding problems involving acceleration is Newton's Second Law:- \(F_{net} = m \cdot a_{net}\) - where \(F_{net}\) represents the sum of all forces, and \(a_{net}\) is the resulting acceleration.
In the given exercise, the object's acceleration is given as \(9.4 \, \text{ms}^{-2}\), slightly less than \(g = 9.8 \, \text{ms}^{-2}\). This indicates the effect of air resistance reducing the acceleration.