Presentation on theme: "Forces Change Motion Force- push or a pull"— Presentation transcript:
1 Forces Change Motion Force- push or a pull Can speed up or slow down the motion of an object or change its direction without changing its speed.
2 Have a size and direction Forces are VECTORSHave a size and direction
3 Balanced Forces Ex: Physics book at rest on a table top. Two forces are acting upon the book.Gravity pushes down on the book.The table pushes up on the bookBoth forces are equal in size/magnitude/number and opposite in direction
4 Balanced Forces- The forces are balanced The book is said to be at equilibrium.No unbalanced force acting upon the bookWhen all the forces acting upon an object balance each other, the object will be at equilibrium; it will not accelerated.
5 Balanced Forces A person standing upon the ground. Two forces acting upon the person.Gravity exerts a downward force.The floor of the floor exerts an upward force.
6 Balanced Forces These two forces are of equal magnitude/size In opposite directionsThey balance each other.The person is at equilibrium.There is no unbalanced force acting upon the person
7 Balanced vs. Unbalanced Forces Net Force- The overall force acting on a object when ALL the forces are combinedIf the NET FORCE is ZERO all of the forces acting on the object are zero.
8 Balanced vs. Unbalanced BALANCED forces are the same as having no force at all.The motion of an object doesn’t change
9 Change the motion of an object Unbalanced ForcesChange the motion of an object
10 Balanced vs. Unbalanced If one of the basketball players pushes with a grater force than the other player, the ball will move in the direction that player is pushing.The motion of the ball changes because the forces on the ball are UNBALANCED.
11 Balanced forces Don’t change an object’s speed or direction A unbalanced force is needed to change an object’s motion
12 Sir Isaac Newton lived during the 1600s His laws of motion explain:RestConstant motionAccelerated motionDescribe how balanced and unbalanced forces act to cause these states of motion.
13 Sir Isaac Newton Built his ideas on Galileo Galilei’s ideas Newton’s 3 Laws of Motion
14 Newton’s First LawObject at rest remains at rest, and objects in motion remain in motion with the same velocity, unless acted upon by an unbalanced force.
15 Newton’s First LawThe ball is in motion with the same velocity, unless acted upon by an unbalanced force.
16 Have you ever been riding in a car when the driver suddenly slammed on the brakes? How did your body move as the car came to a stop? You probably felt your body move forward..
17 When you felt this happening you experienced Newton's first law of motion. Newton's first law of motion says that an object in motion will stay in motion and an object at rest will stay at rest unless acted on by an unbalanced force
18 Newton called his first law inertia. In the car your body was in motion, traveling at the same speed as the car. When the car stopped, your body stayed in motion. If you were not wearing a seatbelt and you were traveling very fast, your body could continue to move forward through the windshield!
19 Try the following activity to demonstrate this law! Place a 3x5 card on top of a glass.Put a coin on the center of the card.Flick the card horizontally with your finger.What happens to the coin?Explain what happened to the coin using Newton's first law.
20 InertiaResistance of an object to change in the speed or direction of its motionNewton’s first lawWhen you measure the mass of an object you are also measuring its inertiaIt is easier to push or pull an empty box than the same box when it full of books
21 Main Ideas Objects tend to stay at rest unless something hits them. Things keep on doing what they are doing unless something hits them.Inertia- the name given to an object’s tendency to keep doing what it is doing
22 ForceMass x AccelerationF= m x aUnits are Newtons (N)kg x m/s2
23 Newton’s 2nd LawThe acceleration of an object increases with increased forceDecreases with increased massIs in the same direction of the force
24 Newton’s 2nd Law- Ties Together- Force, Mass, Acceleration Acceleration of an object depends on the mass of the object and the size of the force appliedIf an object loses mass, it can gain acceleration if the force remains the same
25 Newton’s 2nd LawAcceleration of an object increases with INCREASED FORCE and decreases with INCREASED MASS.The direction in which an object ACCELERATES is the same as the direction of the force.
26 Newton’s 2nd LawWho is exerting the most force behind the cart?
27 Newton’s 2nd Law Which cart has the largest mass? Which is the easiest to push?
28 Main Ideas- Newton’s 2nd Law Small mass leads to LARGE accelerationLarge mass leads to SMALL acceleration
29 A net force acting on an object causes the object to accelerate. Main IdeasA net force acting on an object causes the object to accelerate.A net force acting on an object causes an object to accelerate.
30 Centripetal Force Any force that keeps an object moving in a circle This force points toward the center of the circleWithout this force object would go flying off in a straight lineCentripetal force keeps the planets in orbit
31 Spinning stuff- Centripetal Force Spinning a bucket of water over your head without spilling a drop, you are also applying a centripetal force. If you let go of the bucket, it will move in a straight lineCentripetal force is always directed at the centre of an object.
33 Centripetal Force Greater acceleration = greater centripetal force More mass requires more centripetal force to have the same circular speed as a less massive object.No matter the mass of an object, if it moves in a circle, its force and acceleration are directed to the center of the circle
34 Newton’s 3rd LawFor every action, there is an equal and opposite reactionAction and Reaction ForcesRockets going into spaceSquid and Jellyfish movement
39 Momentum Found in moving objects Measure of mass in motion p= mv momentum = pm= massv= velocityUnits kg x m/s
40 Momentum More mass= more momentum Momentum depends on mass Momentum takes into account velocityIs a vector (has size and direction)
41 CollisionTwo objects in close contact exchange energy and momentum
42 Conservation of Momentum Total momentum of a system of objects do not change, as long as no outside forces are acting on that systemTo find total momentum of objects moving in the SAME direction, add the momenta of the objects.Objects traveling in opposite directions, subtract the momentum from one another.