# Balanced and Unbalanced Forces. Balanced and Unbalanced forces.

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Balanced and Unbalanced Forces

Balanced and Unbalanced forces

 Force is measured using the SI ( International System of Units ) unit of newton (N).This is named after Sir Issac Newton. This unit is used to measure the strength of a force.

 If the two objects are the same size but in opposite directions, they will balance out. These forces are called balanced forces

 Sumo wrestling Sumo wrestling

 In a game of tug of war when both the teams pull the rope with equal and opposite forces, then the rope remains stationary as the forces acting on it are equal and opposite and their resultant is zero.

 If the block is pulled from both sides with the same effort the block remains stationary. The forces are equal and opposite and therefore the block does not move. The resultant of the forces acting on the body is zero.

 If you squeezed a rubber ball between the palms of your hands. What would you observe? The shape of the rubber ball changes. The forces applied on the ball are equal and opposite and the resultant of these forces does not move the object, instead the object gets deformed as long as the force is applied. This is a temporary deformation.

 Since these two forces are of equal magnitude and in opposite directions, they balance each other. The person is at equilibrium. There is no unbalanced force acting upon the person and thus the person maintains its state of motion.

 Forces that produce a nonzero net force ( the overall force on an object when all the individual forces acting on it are added together), which changes an object’s motion.

 The figures show a block of wood on a table. When the block is pulled at point A, it begins to move towards the left and if the block is pulled at the point B it moves towards the right.

 Balanced and unbalanced forces Balanced and unbalanced forces

 Balanced and Unbalanced Demonstration Balanced and Unbalanced Demonstration

 Push and ____ are forces.  The force of gravity pulling towards the Earth is called _______  An object placed in water has a force called _______ pushing up on it.  When the forces acting on an object are equal and opposite, they are called _______  If the forces are balanced, the object will stay still or carry on at the same speed in the same direction.

 A. stay in the same place  B. move in the direction of the larger force  C. move in the direction of the weaker force

 A. stay still  B. slow down  C. carry on at same speed in the same direction

Study !!! Study!!!! Study!!!!!!

 The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

 F = ma  The equation form of Newton's second law allows us to specify a unit of measurement for force. Because the standard unit of mass is the kilogram (kg) and the standard unit of acceleration is meters per second squared (m/s 2 ), the unit for force must be a product of the two -- (kg)(m/s 2 ). This is a little awkward, so scientists decided to use a Newton as the official unit of force. One Newton, or N, is equivalent to 1 kilogram-meter per second squared. There are 4.448 N in 1 pound.

 If you want to calculate the acceleration, first you need to modify the force equation to get a = F/m. When you plug in the numbers for force (100 N) and mass (50 kg), you find that the acceleration is 2 m/s2.

 If two dogs are on each side, then the total force pulling to the left (200 N) balances the total force pulling to the right (200 N). That means the net force on the sled is zero, so the sled doesn’t move.

 This is important because Newton's second law is concerned with net forces. We could rewrite the law to say: When a net force acts on an object, the object accelerates in the direction of the net force. Now imagine that one of the dogs on the left breaks free and runs away. Suddenly, the force pulling to the right is larger than the f­orce pulling to the left, so the sled accelerates to the right.  What's not so obvious in our examples is that the sled is also applying a force on the dogs. In other words, all forces act in pairs. This is Newton's third law -- and the topic of the next section.

 For every action there is an equal and opposite reaction.

 Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

 If two forces are acting on an object in opposite directions, the object will move in the direction of the larger force