19 Examples Of Unbalanced Force


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

Examples of unbalanced force

The motion of a car 

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

examples of unbalanced force
Image credit: https://pixabay.com/photos/camaro-car-chevrolet-vehicle-road-5992333/

Firing a bullet

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

Gun fire Image credit: “Live fire exercise” by The U.S. Army is licensed under CC BY 2.0

Launching a rocket

In a rocket launch, fuel-burning creates an unbalanced thrust force that overcomes the earth’s gravity. A rocket stores fuel in the form of fuel stages; with each burning step, the rocket’s weight starts to decrease, and the rocket’s velocity starts to increase. Rockets accelerate in the upward direction opposite to that of gravity by producing more and more thrust.

Launching a rocket Image credit: https://pixabay.com/photos/rocket-launch-rocket-take-off-67643/

Bird flight

Bird’s flight is the most complicated type of locomotion. It is a combination of hovering, flapping, gliding, etc. Birds fly against the force of gravity by flapping wings in the air. Bird wings act like an airfoil (curved shape of wings), which reduces drag force, causing friction and turbulence and help to move forward direction. By flapping wings, the air is pushed in a downward direction that creates lift. Lift force is the unbalanced force that works against gravity, and thrust works against the drag force.

Image credit: https://pixabay.com/photos/seagull-bird-sky-flying-gull-3465550/

Throwing a ball

Throwing a ball is also an example of a projectile motion. When we throw a ball against the force of gravity, it continues its activity until it has kinetic energy to do work against the force of gravity. At maximum height, kinetic energy is converted into potential energy; gravity pulls the ball towards the earth’s surface. In the whole process, an unbalanced force of gravity is acting on the ball, so the ball accelerates downward.

Image credit:https://pixabay.com/photos/juggle-balls-sinai-in-the-air-4919335/

Swimming

The forces involved in swimming are gravity, buoyancy force, thrust, and drag force. In swimming, the buoyancy force, applied by water, balances the gravitational force. Thrust force is created by pulling the water with hands and kicking water backward by legs. Thrust helps to overcome the drag force and to move forward in the water. Water resists the swimmer from moving in the forward direction. It mainly depends on the swimmer’s shape and size; bigger the size and shape, have more resistance to move forward. By creating more thrust force than a drag force, swimmers can swim.

Image credit:https://pixabay.com/photos/swimming-athlete-pool-competition-3608948/

Walking

In the rest position, all the forces on a person are in balanced condition. In walking, a normal reaction, provided by the surface, balances the weight of a person. The force that gets unbalanced is the friction force between feet and floor and the forward-moving force.

Image credit:https://pixabay.com/photos/legs-shoes-walking-walk-path-2635038/

Rolling an object

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

Image credit:https://pixabay.com/vectors/black-down-hill-adult-design-32875/

Rotation in fan

In rotational motion, the inertia of a body plays a vital role. Inertia resists the rotation of an object in rotational motion. In a fan, torque overcomes the resistance of inertia of the body and performs rotational motion. Angular acceleration is perpendicular to the plane of a rotating fan.

Image credit : https://pixabay.com/photos/ceiling-fan-fan-blow-metal-air-571307/

Revolution of the earth around the sun

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

Pirouette

A pirouette is an act of spinning on one foot in ballet dance. In a pirouette, a dancer turns on one leg by raising the other. Dancer rotates around the axis, passing through his head and a supporting leg. The forces involved in the pirouette are the weight of the dancer, normal reaction, torque, and friction between leg and floor. A normal reaction balances weight. Torque and friction are the unbalanced forces in the pirouette. When the dancer turns on his leg, friction stops the motion, but torque overcomes the friction and allows the dancer to perform a pirouette.

Image credit: “The Nutcracker” by Larry Lamsa is licensed under CC BY 2.0

Ice skating

A person can glide on the ice surface by using a specially customized metal blade skate. Metal blades skates reduce the friction between the ice surface and legs and help gain speed, turn, and glide by pushing the ice surface. As the friction is almost zero, an unbalanced force created by pressing the surface of the ice accelerates a skater in the forward direction.

Image credit: “Ice Skates” by Benson Kua is licensed under CC BY-SA 2.0

The sinking of an object

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

Image credit: “Sinking Ship 001” by tony.evans is licensed under CC BY-ND 2.0

Pushing a heavy box

To displace a heavy box from its position, we give it a push. Box remains at its place until the applied force exceeds the static friction between surface and box because static friction is self-adjustable. As soon as external force exceeds friction, the object starts to move in the force direction. Other forces such as gravitational force and normal reaction are in balanced condition.

Image credit: Free Clip Art, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Weightlifting

Weightlifting is a popular sport all over the world. It 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 using an unbalanced external force, all the forces on the weight are balanced.

Image credit:https://pixabay.com/photos/man-person-power-strength-strong-1282232/

See-Saw

In see-saw, we push the ground to overcome gravity. What will happen if we stop applying push against the floor? In that case, we can experience two scenarios. In the first scenario, if both persons have the same weight, a see-saw lever gets balanced, and both come to rest. In the second scenario, one person is heavier than the other, then the heavier person gets down due to his weight and lighter one in the up position, and again a balanced condition is acquired. Hence to play a see-saw, one must apply the unbalanced force by pushing against the ground.

Image credit: “See-saw (1940s? 50s?)” by pellethepoet is licensed under CC BY 2.0

Bungee jumping

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

Image credit: “Bungee Jumping at the Pearl Qatar” by SJByles is licensed under CC BY-SA 2.0

Pendulum

In the oscillatory motion of a pendulum, an unbalanced force is provided by the component of gravitational force. At its mean position pendulum is at rest; all the forces such as the bob’s weight and the tension in the string are in a balanced condition. But when we displace the pendulum from its mean position, an unbalanced restoring force, i.e., component of gravity, starts building in the opposite direction of displacement. The restoring force accelerates the pendulum and allows it to oscillate about its mean position.

Image credit: https://pixabay.com/photos/hypnosis-clock-pocket-watch-4041582/

Kicking a football

An external force is applied to accelerate a soccer ball. Many different forces are acting on a football, such as gravitational force, the normal force provided by the ground, air resistance, friction between ball and ground, etc., are balanced in its rest position. A soon as we apply an external force, all the forces get unbalanced, and the ball starts to move.

We all have seen a banana kick, which curves the ball flight, in a football. In a banana kick, the ball needs to kick properly to rotate in its flight. Due to that rotation, the higher air pressure is generated on the opposite side of spin while low pressure is generated along the same direction of spin. That allows the ball to curve towards the lower pressure zone. This phenomenon is called the Magnus effect, and this phenomenon occurred due to unbalanced forces.

Image credit: https://pixabay.com/photos/football-child-shot-soccer-to-play-4392446/

Tug-of-war

We all have played this game in our childhood. It’s a straightforward game with just one rule, i.e., to drag the opposite team across the centerline. If both teams apply the same force, then the force from both sides gets balanced so that the rope will remain at the centerline, and war will never end. But if there is the slightest variation in the forces, then the team with more force drags the other team in their direction.

Image credit: “Tug of War” by Robert Louis Clemens is licensed under CC BY-ND 2.0

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Shambhu Patil

I am Shambhu Patil, a physics enthusiast. Physics always intrigues me and makes me think about, how this universe works? I have an interest in nuclear physics, quantum mechanics, thermodynamics. I am very good at problem solving, explaining complex physical phenomenon in simple language. My articles will walk you through each and every concept in detail. Join me over LinkedIn to https://www.linkedin.com/in/shambhu-patil-96012b1a1 . E-mail :- shambhupatil1997@gmail.com

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