FORCE AND MOTION UNIT

1. FORCE AND MOTION UNIT Have you ever wondered why objects move faster than others? Why do objects fall to the ground? Why some cars, boats, or planes go slower than others?

2. Forces Have you ever wondered why and how objects begin to move and why objects stop all of a sudden? An object starts to move, stops moving, or changes directions ONLY when a force acts on it. Some forces act on objects directly and some forces act on objects indirectly. For example, when you push on a door, you directly apply the force that makes the door open. Other forces, such as gravity, act on objects at a distance.

3. THE STRONGER THE FORCE THE MORE AN OBJECT WILL MOVE. THE HEAVIER THE OBJECT, THE MORE FORCE YOU MUST USE IN ORDER TO MOVE THE OBJECT. IF YOU PUSH AN OBJECT A LITTLE THE OBJECT WILL ONLY MOVE A SHORT DISTANCE BUT IF YOU PUSH AN OBJECT WITH A LOT OF FORCE THAN THE OBJECT WILL TRAVEL FARTHER.

4. Motion is all around you. Its even inside your body as your blood moves. For every motion, there is a force which makes something move. Motion is the act of moving from one place to another or changing direction or position of object. Motion can be measured using a compass or the directions north, south, east, and west. A force can cause an object to move or stop moving, change direction or speed. Force is a push or a pull of an object. Nature can also be a strong force. Breezes, ocean waves, earthquakes are all examples of force moving an object. Pushing and Pulling forces change the position and motion of all objects. Motion, Direction, and Force

6. 3 Laws of Motion by Sir Issac Newton (1687) Much of what we know about motion comes from scientists who lived hundreds of years ago. They conducted tests on moving objects. British scientist Isaac Newton discovered gravity. Gravity is the invisible force that causes all objects to fall toward the ground. You may have heard he was sitting under a tree one day when a falling apple hit him on the head.

7. Friction: • As a soccer ball moves along the grass, the grass acts on it in the opposite direction, pushing against the ball and slowing it down. This force is called friction. • Friction can be useful, for example, the tires on cars must be able to grip the road so that the car can change speed or turn. The friction on the tires make the car safe to drive. When the tires are worn down, there are not enough friction on the tires.

8. Newton’s First Law of Motion Object in motion Object at rest Isaac Newton is known for his three laws of motion, which explain how things move. The first part of the law says that an object in motion will remain in motion, and an object at rest will remain at rest unless a force acts upon it. This is called inertia. All objects, at rest or in motion, has inertia. Inertia is what makes an object keep doing what it is already doing.

9. What is motion? • We know that “motion” is any object that is moving. • We know that we describe motion in 3 ways: • HOW it moved • The DIRECTION it moved • The SPEED it moved

10. HOW does something move? • To move something, a “force” has to happen. • A FORCE is a push or a pull • To get a toy car to move, the force of pushing is applied as we push it across the floor.

11. How does something stop? • We can get it to move, but now how do we get it to stop? • An object will stop when it loses speed or “momentum.” • An object will stop when a “force” acts and stops it. • Our toy car stops when it runs into the wall. • What else makes something stop…

12. FRICTION • We know that friction can help objects stop. • Friction is when 2 objects rub together.

13. Friction • Friction can help you-tennis shoes on the gym floor so you have grip and won’t fall down.

14. Friction • Friction can hurt you-sock feet on the dance floor and you slide into a wall. • The friction from the carpet and wheels on the toy car help it lose speed, slow down, and stop.

15. What about when an object is at “rest”? • An object is at rest when it is still. • A force is still acting on the object to keep it still and keep it in place.

16. What is it? • GRAVITY • Gravity pulls objects DOWN. • Gravity is what keeps you in your seat, brings your ball back down, and you back down after you jump.

17. What else is there? • We know how something moves and how something stops. • We know that a force is a push or pull that makes things move. • We know friction is 2 objects rubbing together. • We know gravity pulls/pushes everything back down. • There’s more to motion-Let’s find out…

18. Newton’s First Law of Motion • You have a hockey puck • It is not moving, it is at rest • To get the puck to move, you have to do something to the puck like hit it. This is the force. • Without the force, it will stay in the same spot and be at rest. • Watch this to learn more! ..\Desktop\Newton_s_First_Law_of_Motion.asf

19. Newton’s 1st Law of Motion-1st part • “An object at rest remains at rest unless acted on by another force.” • An object will stay at rest or “look still” until you do something to make it move. • The toy car stays at the starting line (at rest) until you push it (apply a force). • The hockey puck sits on the ice (at rest) until you push it with the stick (apply a force).

20. Newton’s First Law of Motion • Think of a train-that train drives down a straight track and stays going in a straight direction.

21. Newton’s 1st Law of Motion • What happens when the track curves left or right? • The train turns and goes left or right

22. Newton’s 1st Law of Motion-2nd part • “An object in motion in a straight line tends to say in motion in a straight line unless acted upon by another force.” • An object will go straight until a force makes it go another direction. • Your paper airplane flies straight until gravity pushes it down. • Thomas drives straight until the driver makes it “turn” with the track.

23. Example of Inertia: • When are driving on the road and the car is going 40 mph, all of a sudden, you hit another car. The car stops because the force of the other car stops it but your body keeps traveling at the same speed of 40 mph. That is inertia. Seatbelts and airbags were invented because we know that the law of inertia will keep your body in motion. Seatbelts and airbags save lives.

24. Another Example of inertia HAVE YOU EVER SEEN A MAGICAN PULL A TALBECLOTH OUT FROM UNDER DISHES AND THE DISHES STAY PUT? SINCE THE DISHES HAVE INERTIA, THEY STAY PUT AND ONLY THE TABLECLOTH MOVES BECAUSE THE FORCE (PULL) IS ONLY APPLIED TO THE TABLECLOTH, NOT THE DISHES!!!

25. Newton’s Second Law of Motion • Mass is the amount of matter in an object and Newton’s second law deals with mass and motion. • An objects motion depends upon its mass and the amount of force needed to move that mass. • Why is it easier to move a small rock than a boulder? • Since a boulder has more mass than a small rock, much more force is needed to overcome the boulders inertia. Much less force is needed to make small rocks move, stop, or change direction. More force, more inertia Less force, less inertia

26. Second Law of Motion Deals With Speed • Speed measures how far something travels on a certain amount of time or use the formula • speed = distance divided by time. • The faster an object moves, the more force is needed to stop it!!! EX: What is the speed of a car traveling 225 miles in 3 hours You can measure speed with a clock or stopwatch will measure time and speed. Scientist can calculate speed by dividing distance over time.

27. Velocity Velocity measures distance over time like speed but it also includes direction. Often times the direction is measured, using north, south, east, and west. You can measure velocity with a compass. This tells what direction something is traveling. For example, the boat moves 20 miles per second across the water going south towards Florida.

28. Momentum is the amount of force in a moving object. Momentum is the product of mass and velocity of an object. Momentum is changed by how fast an object is moving and how much mass the object has. The greater the mass, the more momentum (speed) an object has. EX: If you had two moving vehicles, a train and a scooter, the train would have more momentum because it has a lot of mass. So a great deal of force will be needed to overcome the inertia of the train’s motion and make it stop!!! Speed and Momentum Train Vs. Scooter

29. Question for Momentum Which would have more momentum, a baseball thrown soft and gently or a baseball thrown hard and with a lot of force? The baseball thrown with a lot of force will have greater velocity and have greater momentum. Velocity can give even small objects a lot of momentum.

30. Acceleration When an object starts, stops, speeds up, slows down, or when an objects turns, it changes direction (velocity) is called acceleration. Suppose you are riding a bike, when you start pedaling, you accelerate, when you turn a corner, you accelerate because you are changing direction. Finally when you stop the bike you accelerate because the speed changes. The only time you are not accelerating is when you are riding in a straight line at the same speed!!!

31. Newton’s Third Law of Motion (Friction) The box is 20 pounds • Newton’s third law of motion says that for every force or action, there is an equal force and opposite reaction. • Example: if you lift a 20 pound box, the box pulls down because of gravity so you must lift the box with an equal force of 20 pounds in the opposite direction to overcome the gravity and get the object to move! The box pulls down with an equal force of 20 pounds

32. Forces Change Motion The motion of an object depends on the force acting on that object. Thrust, Drag, and Lift are forces that affect the motion of an object. Thrust is the force that moves an object forward. Drag happens in the opposite direction of force and slows down an object in motion. Lift is another force that pushes objects up and is created by force and pressure. Maintaining a steady flight requires a balance, often described as an equilibrium of all the forces acting upon an airplane. If lift becomes greater than weight, then the plane will accelerate upward. If the weight is greater than the lift, then the plane will accelerate downward. When the thrust becomes greater than the drag, the plane will accelerate forward. If drag becomes greater than the thrust a deceleration will occur. Acceleration is best explained by using Newton's Second Law of Motion.

33. In science, work happens when you move something. The amount of work you do depends on the distance the object moves and the force it takes to move it. Force x distance= work Energy is the ability to do work. The more energy you have, the more work you can do. There are two kinds of energy, potential and kinetic. Force, Motion, and Work

34. Potential and Kinetic Energy POTENTIAL ENERGY: IS STORED ENERGYIN AN OBJECT. EXAMPLE: HOLDING A BASKETBALL IN YOUR HAND. KINETIC ENERGY: IS ENERGY IN MOTION. EXAMPLE: DRIBBLING A BASKETBALL.

36. Net Force with Balance and Unbalanced Forces. Net force is the total force acting upon an object. For example, when an object is resting on a table it is balanced and has a net force of zero and the apple is not moving. Net Force is measured in newtons.

37. Practice Questions: 1. What is needed to change the direction of a moving mass? 2. What happens to an object moving in one direction? 3. What is friction?

38. 4. What do you think would be the fastest surface for a toy car to travel if pushed with the same force? Practice Questions: A. Ice B. Grass C. Concrete D. Carpet

39. 5. What slows an object Practice Questions: A. speed B. friction C. gravity D. momentum

40. Practice Questions: 6. Two toy race cars are going to be raced down the same ramp. Which information is most helpful in predicting which car will win the race? A. Length of ramp B. Volume of the cars C. Slope of the ramp D. Mass of the cars volume of the cars slope of the ramp mass of the cars

41. 7. Which is the best example of a pushing force that reduces the speed of an object? A ball hitting a baseball A break rubbing against a wheel A Pedal turning the wheels of a bike A skateboard wheel rolling against pavement. Practice Questions:

42. 8. Sometimes machines are used to lower heavy object from the top of the building to the ground. What is most responsible for making the object move to the ground. Practice Questions: A. wind B. gravity C. friction D. Momentum

43. 9. Why is it important for basketball players to wear shoes with treads? Practice Questions: A. to increase the speed of the player B. to decrease the force between the player and the floor C. To increase friction between the floor and the player’s feet D. To decrease the amount of force needed for the player to move

44. 10. A group of six people are on a boat. There are three people in the front and three in the back. The front of the boat is sinking lower than the back of the boat. Which best explains why the front of the boat is sinking? Practice Questions: A. There are heavier items in the back of the boat. B. The pressure of the water is greater against the front of the boat. C. The people in the front of the boat are closer. D. The people in the front of the boat are heavier.

45. Practice Question for Momentum 11. Which would be harder to stop, a toy truck moving in a straight line at 50 mph or a real truck with the same velocity?

46. What is the speed of a train traveling 100 miles in 2 hours? Practice Question for Speed

47. Practice Questions, True or False 13. For every force, there is a motion?_______ 14. For every motion, there is a force?_______ 15. Forces and motion have the same meaning?_______ 16. People and nature produces forces, while machines produce motion. _________

48. Practice Questions: 17. Name and describe Newton’s 3 laws of motion.

49. Practice Questions: 18. If a friend bumps into the side of you while you are skating in a straight line, what will happen to your motion? 19. For every action in one direction____ A. a weaker force acts in the same direction B. An equal force acts in the opposite direction. C. A stronger force acts in the opposite direction. D. An equal force acts in the same direction.

50. Practice Question: • 20. If you pull a rubber band back but you don’t release it , what kind of energy does the rubber band have?