The vector sum of forces that act on a body is the magnitude of resultant force. At a given time, there are always multiple forces working on a body. Either they act in the same direction or the opposite directions. The combination of all the forces keeps the object stable and does the work. In physics, the single force that generates the same effect as multiple forces are known as the magnitude of the resultant force.
Force, being a vector quantity, is important to consider the direction of a force. The forces that act in the same direction are taken as positive, and those acting in opposite directions are negative. The restaurant force is also known as the net force. Two to three people are required to lift a heavy box. But if there is an extremely strong bodybuilder, he can easily lift the box.
Hence the force exerted by the bodybuilder would be almost equal to the force exerted by all the other people. And it would be the magnitude of resultant force. When the force on the body acts in the opposite direction, they are subtracted to generate the net force. When the force acts in a particular direction, they add up to get the magnitude of the resultant force. When the net force acting on a body equals zero, it is known as balanced force.
Here forces are equal in magnitude but act in the opposite direction. If the force is balanced, the body will continue to remain in the position of rest or motion. There would be no acceleration. In the above diagram, we can see that the weight of the body pulls it downwards, but due to the tension on the rope, it does not fall.
Hence the magnitude of the resultant force acting on the body is zero. Even the log floating on water is possible due to the balanced force. The weight of the log acts downwards, but the upthrust pulls it upwards. Hence the net force is zero, and the log floats on water.
If the weight exceeds the upthrust, then the log will sink into the water. Speed is also mentioned in reference to something. Now to answer your question, I will take two cases, one in which the object is at rest and one in which the object is in motion relative to you. Case 1: Imagine a small car that is standing in the neutral gear and has the handbrake disengaged. If a person and his friend are equal in strength and if the person pushes the car from behind and his friend pushes the car from ahead and if they both push the car with same force, the car will not move an inch as both of them would be canceling each other's force.
Case 2: Now imagine the car and the two people doing their pushing on a train that is moving at a constant speed in a constant direction. Let the railway track be frictionless and imagine yourself standing beside the railway track and watching the two people push the car.
You would see the car moving at a constant speed but you would not notice any change in the speed of the car. To the two people on the train, it would seem as if the car is still but to you the car would appear to be moving at a constant speed.
So it is simply a matter of perspective because nothing is ever truly in motion if we don't mention the point of reference. For an object to change from its state of rest to motion needs some force. When a force is applied the velocity of the object changes from 0 to some velocity V and it keeps increasing as long as the force is present.
This change in velocity is termed as acceleration. Now if you remove the force, the object will move with the constant velocity V provided no other force is acting on it. For example, we pushed a CART forward and we got to maintain pushing it to keep it moving forever. Then, when we let go it will stop. This is just because there is friction, this friction will cause the cart to stop, remove that and the cart will move forever!
In real life Earth scenario however, this seldom happens, but push a cart in outer space and viola! It says goodbye us! Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
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