How a Simple Push or Pull Changes Everything Around You
Learn how to define force, describe its effects with real-life examples, classify contact and non-contact forces, and explain why objects fall to the ground.
What is force and how does it affect things around us?
A force is a push or a pull that can change the state of motion or shape of an object. In ICSE Class 6 Physics, you will learn how force is present everywhere, from opening a door to dropping a ball. This article covers the definition of force, its units, the effects force can have on objects, the difference between contact and non-contact forces, and why things fall to the ground. By the end, you will be able to explain these concepts clearly and use real-life examples to support your answers.
How do you define force, and what are its units?
Force is defined as a push or a pull acting on a body. A force always has both magnitude (how strong it is) and direction (where it is applied). The S.I. unit of force is the newton (N), named after the scientist Isaac Newton. The gravitational unit of force is the kilogram-force (kgf), which is the force with which gravity acts on a mass of 1 kilogram. For example, when you push a bicycle, you are applying a force in a certain direction; the harder you push, the greater the magnitude. In real life, if you lift a 1 kg bag, the force you feel due to gravity is 1 kgf. Many students mix up mass and force, but remember: mass is measured in kilograms (kg), while force is measured in newtons (N) or kilogram-force (kgf).
What can a force do? Everyday examples that show its effects
A force can produce motion in a body at rest, stop or slow down a moving body, change its speed, alter its direction, or change its shape or size. For example, kicking a football at rest makes it move (producing motion). When you press the brakes on a bicycle, you slow it down or stop it. Pushing a swing harder increases its speed, while pulling the string of a bow changes the direction of the arrow. Squeezing a rubber ball changes its shape. In real life, opening a jammed door (changing its state of rest), catching a cricket ball (stopping it), or stretching dough (changing its shape) are all effects of force. A common misconception is that force is only needed to start motion, but force can also stop or change ongoing motion.
How do you tell contact forces from non-contact forces? With examples
Contact forces act only when two objects are physically touching each other, while non-contact forces act even when objects are not in contact. Muscular force (like lifting a bag) and friction (like rubbing your hands together) are examples of contact forces. Gravitational force (the earth pulling objects down), magnetic force (a magnet attracting iron), and electrostatic force (a charged comb attracting bits of paper) are non-contact forces. For example, when you push a table, your hand must touch it, so it is a contact force. When a magnet attracts a pin from a distance, it is a non-contact force. Students often think all forces require contact, but gravity and magnetism show that forces can act at a distance.
What is the weight of a body, and why do things fall to the ground?
The weight of a body is the force with which the earth attracts it towards itself. This force is called gravity. When you release an object from a height, it falls towards the earth because of the gravitational force acting on it. For example, if you drop a pencil, gravity pulls it down, giving it weight. The weight of an object depends on its mass and the force of gravity. In real life, this is why fruits fall from trees or why a ball drops to the ground when thrown up. A common mistake is to confuse weight with mass: mass is the amount of matter in an object (measured in kg), while weight is the force of gravity on that mass (measured in newtons or kilogram-force).
Exam tip
The mistake most students make with force units
Many students confuse mass (kg) with force (N or kgf). For example, they might write the weight of a 2 kg object as '2 kg' instead of the correct '2 kgf' or its equivalent in newtons. Remember: mass is always in kilograms (kg), but force must be in newtons (N) or kilogram-force (kgf). Always check the unit you are using when answering questions about force or weight.
Did you know
Who is the newton named after?
The S.I. unit of force, the newton (N), is named after Isaac Newton, who explained how forces work and how gravity pulls objects towards the earth. His work helps us understand why things move, stop, or fall, and his name is used for the unit of force in physics.
Key takeaways
What to remember about force
- Force is a push or a pull, has magnitude and direction, and its units are newton (N) and kilogram-force (kgf).
- Force can move, stop, speed up, slow down, change direction, or change the shape of objects—seen in everyday actions like kicking, braking, or squeezing.
- Contact forces need touching (like muscular force, friction), while non-contact forces act at a distance (like gravity, magnetism, electrostatics).
- The weight of a body is the force with which earth attracts it, and gravity makes things fall towards the ground.
Test yourself with a few examples from your daily life to see if you can spot which force is acting and what effect it has.
- Force can move, stop, speed up, slow down, change direction, or change the shape of objects—seen in everyday actions like kicking, braking, or squeezing.
- Contact forces need touching (like muscular force, friction), while non-contact forces act at a distance (like gravity, magnetism, electrostatics).
- The weight of a body is the force with which earth attracts it, and gravity makes things fall towards the ground.
Test yourself with a few examples from your daily life to see if you can spot which force is acting and what effect it has.