Balanced and Unbalanced

GPS S8P3. Students will investigate relationship between force, mass, and the motion of objects. b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.

EQ  What is the difference between balanced and unbalanced forces?  What is a force?

Force  Is a push or a pull A force can give energy to an object causing the object to 1.Start moving 2.Stop moving 3.Change its motion

Force is expressed using a unit called Newton (N)

Balanced Forces  Forces work in pairs and can be either balanced or unbalanced.  Balances forces do not cause a change in motion, they are equal in size and direction.  What are some examples of balanced forces? 1. _____________________________________ 2. _____________________________________ 3. _____________________________________

Because the force each is exerting is equal, the two forces cancel each Other out and the resulting force is zero. Therefore there is no change In motion. Two equal forces pushing in opposite directions.

Unbalanced Forces  Unlike balanced forces, unbalanced forces always cause a change in motion. They are not equal and opposite.

Unbalanced forces Continued  Unbalanced forces can also be exerted in the same direction.  Imagine your family car has broken down and you and your younger sibling are pushing it. The sum of your forces will move the car in the direction you are applying the force.  Unequal force in same direction = Change in motion.

Net Force  Combination of all the forces acting on an object.  Determining net force depends on the directions of the forces.

Things To Remember 1. Forces in the same direction combine by addition (+) 2. Forces in opposite directions combine by subtraction (-) 3. Balanced forces have a net force of zero.

7 N 5 N Net Force 7 N 5 N = 2 N 7 N 5 N 7 N 5 N = 12 N 1.A net force can also be defined as the overall force acting on an object, when all the individual forces acting on the object are added together. 2. Overall power/energy/physical strength To find the net force – subtract the opposing sides

9 N 7 N 5 N 7 N 5 N = 9 N 3 N 12 – 9 = 3N

Two dogs are pulling on opposite ends of a rope. The dog on the left is pulling with a force of 25newtons. The dog on the right is pulling with a force of 60 newtons. What will be the resulting motion? A The dogs will not move. B The dogs will move toward the left. C The dogs will move toward the right. D Both dogs will move in the direction that they are pulling.

If the forces are acting on the same side of the object, you _____ the numbers 50N 10N Add

If the forces are acting on the opposite sides of the object, you Subtract the numbers 35N 10N Subtract

1. Which direction will the box move – left or right? _______ 2. What amount of force will move the box? _____ 55N 26N

Which direction will the car move? Right due to more force applied

1. What is the total force being applied to the left side of the box? 2. What is the total force being applied to the right side of the box? ___ 3. Which direction will the box move? _____ 4. What amount of force will move the file cabinet? _____ 15N 80N 75N 80N Right 90 – 80 = 10N

Now You Try Some  Two tug boats are moving a barge. Tugboat A exerts a force of 3000 N on the barge. Tugboat B exerts a force of 5000 N on the barge in the same direction. What is the combined force?

Answer  Because they are exerting a force in the same direction, we add the two forces together.  3000 N N = 8000 N

Let’s Try One More  Now suppose Tugboat A exerts 2000 N on the barge while Tugboat B exerts 4000 N in the opposite direction. What is the combined forces exerted on the barge?

Answer  Because the forces are opposite, we subtract N – 2000 N = 2000 N