Unbalanced Force

The force required to change the state of motion of an object is called unbalanced force. When two or more forces of unequal magnitude act on an object, it changes the position of the object which is an example of unbalanced forces. There are many examples of unbalanced forces around us that we see and experience in daily life. Here we are going to discuss those examples of unbalanced force.

examples of unbalanced force

  • speed of a car
  • shot put
  • launch rocket
  • bird flight
  • throwing a ball
  • swimming
  • Walking
  • rotate an object
  • fan spin
  • Earth’s revolution around the Sun
  • pirouette
  • ice skating
  • sinking of something
  • pushing a heavy box
  • lifting weights
  • see-saw
  • Bungee Jumping
  • anchor
  • kicking a football
  • tug of war

speed of a car 

When a car is in motion, some of the forces acting on the car are unstable. The forces acting on the car are gravitational force, normal reaction, friction force, engine driving force, etc. When the driving force of the motor exceeds the friction, the car starts to accelerate. This proves that the driving force and the frictional force are in an unstable state.

Unbalanced Force

shot put

A bullet is a projectile. A bullet filled with gunpowder provides the impulse to a shot at the time of firing. The bullet moves in a downward direction due to gravity and after some time falls on the ground. The unbalanced force responsible for the downward acceleration of the bullet is the force of gravity. Hence, it is an example of an unbalanced force.

Unbalanced Force

launch rocket

In a rocket launch, the burning of fuel produces an unbalanced thrust force that overcomes Earth’s gravity. A rocket stores fuel in the form of fuel stages; With each burning step, the weight of the rocket begins to decrease and the velocity of the rocket increases. Rockets move in an upward direction opposite to gravity by producing more and more thrust.

Unbalanced Force

bird flight

Bird flight is the most complex type of movement. It is a combination of hovering, flapping, gliding etc. Birds fly against the force of gravity by flapping their wings in the air. The bird’s wings act like an airfoil (the curved shape of the wing), which reduces drag force, which creates friction and turbulence, and helps it propel in the forward direction. By flapping the wings, the air is pushed in a downward direction, which creates lift. Lift force is the unbalanced force that acts against gravity, and thrust works against the force.

throwing a ball

Throwing a ball is also an example of projectile motion. When we throw a ball against the force of gravity, it continues its activity until there is no kinetic energy to do work against the force of gravity. At maximum altitude, kinetic energy is converted into potential energy; Gravity pulls the ball towards the surface of the earth. Throughout the process, the unbalanced force of gravity is acting on the ball, so the ball moves downwards.


The forces involved in swimming are gravity, buoyancy, thrust and drag forces. In swimming, the buoyant force exerted by the water balances the force of gravity. Thrust is created by pulling the water with the hands and kicking the water backwards with the feet. Thrust helps to overcome drag force and propel it forward in the water. The water prevents the swimmer from moving in the forward direction. It mainly depends on the size and shape of the swimmer; The larger the shape and size, the greater the resistance to moving. Swimmers can swim by creating more thrust force than drag force.


In a state of rest, all the forces on a person are in a balanced state. In walking, a typical response provided by a surface is balancing the person’s weight. The force that becomes unbalanced is the force of friction between the feet and the floor and the forward force.

rotate an object

There are two simultaneous actions in a rolling motion: rotation and translation motion. The forces responsible for rolling motion are weight, normal reaction, friction, and external torque: unbalanced torque and frictional forces cause an object to roll. Torque overcomes friction, and because of that, objects tend to roll on the floor. The rolling motion stops when both the friction force as well as the torque force are balanced.

fan spin

In rotational motion, the inertia of the body plays an important role. Inertia opposes the rotation of an object in rotational motion. In a fan, torque overcomes the body’s resistance to inertia and performs rotational motion. The angular acceleration is perpendicular to the plane of a rotating fan.

Earth’s revolution around the Sun

In this motion, the Earth is constantly changing the direction of its linear velocity. From this we can say that the planet is moving around the Sun. According to Newton’s law of motion, an unbalanced force is required to change the state of motion; The gravitational pull of the Sun provides that necessary force which is called centripetal force. The direction of centripetal force and acceleration of the earth is always the same towards the center of the orbit.


A pirate ballet is an act of spinning on one leg in dance. In a pirouette, a dancer turns on one leg by lifting the other leg. The dancer rotates around the axis, passing through his head and a supporting leg. The forces involved in searing are the dancer’s weight, general reaction, torque and friction between the foot and the floor. A typical reaction is balancing the weights. Torque and friction are unbalanced forces in the pirouette. When the dancer moves her foot, the friction stops the motion, but the torque overcomes the friction and allows the dancer to perform a pirouette.

ice skating

A person can glide across the surface of the ice using a specially adapted metal blade skate. Metal blade skates reduce friction between the ice surface and the feet and help to achieve speed, turn and glide by pushing off the surface of the ice. Since friction is almost zero, the unbalanced force produced by pressing on the ice surface causes a skater to accelerate in the forward direction.

sinking of something

When the buoyant force and the gravitational force are not balanced, the object may sink in water. According to Archimedes, the buoyant force depends on the fluid density and the submerged volume of a body. So to float to the surface, we have to take care of these two factors. Therefore a necessary condition for sailing on a liquid surface is to maintain a balance between gravity and buoyant force.

pushing a heavy box

To displace a heavy box from its position, we give it a push. The box remains in place until the force applied exceeds the static friction between the surface and the box because the static friction is self-adjustable. As soon as the external force is greater than the friction, the object starts moving in the direction of the force. Other forces such as the force of gravity and the normal reaction are in equilibrium.

lifting weights

Weightlifting is a popular sport all over the world. This is a classic example of an unbalanced force. In weightlifting, a person lifts a dead weight by applying an unbalanced force to overcome the force of gravity. Before applying an unbalanced external force, all forces on the load are balanced.


In saws we push the ground to overcome gravity. What happens if we stop pushing on the floor? In that case, we can experience two scenarios. In the first scenario, if both individuals have the same weight, the sight-seeing lever is balanced, and both come to rest in the second scenario, one person is heavier than the other, then the heavier person falls down due to their own weight and the lighter in an up position, and again a balanced position is achieved. Therefore, to play the saw, an unbalanced force should be applied by pushing it off the ground.

Bungee Jumping

In bungee jumping, the diver is attached to an elastic rope, which provides restorative force opposite to the direction of motion. When a jumper dives from a height, he falls vertically down under the force of gravity until the elastic rope is loosened. After that, a restoring force begins to build up in a string, which eventually stops the downward movement. At one point, the elastic rope stops the jumper’s downward motion and pulls it back. The jumper continuously oscillates up and down until all the energy is dissipated. When the jumper stops oscillating and comes to rest, the restoring force in the rope and the weight of the jumper are balanced.


In the oscillatory motion of a pendulum, an unbalanced force is provided by the component of the gravitational force. The pendulum in its mean position is at rest; All the forces such as the weight of the ball and the tension in the string are in equilibrium. But when we displace the pendulum from its mean position, an unbalanced restorative force, that is, the component of gravity, starts to build up in the opposite direction of the displacement. The reversing force accelerates the pendulum and allows it to oscillate about its mean position.

kicking a football

An external force is applied to accelerate the soccer ball. There are many different forces acting on the football, such as the force of gravity, the normal force provided by the ground, air resistance, friction between the ball and the ground, etc., balanced in its resting position. As soon as we apply an external force, all the forces become unbalanced and the ball starts moving.

We’ve all seen the banana kick in a football, which diverts the flight of the ball. The banana kick requires the ball to be kicked properly to rotate in its flight. Because of that rotation, high air pressure is produced in the opposite direction of spin while low pressure is produced in the same direction of spin. This allows the ball to rotate towards the lower pressure area. This phenomenon is called the Magnus effect, and this phenomenon was caused by unbalanced forces.

tug of war

We all have played this game in our childhood. It is a straight game with only one rule, that is, drawing the opposite team across the center line. If both parties apply equal forces, the forces from both sides are balanced so that the rope remains on the midline and the battle never ends. But if there is even a slight variation in the forces, the team with the greater force pulls the other team in its direction.