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FORCE AND MOTION. 1. Earth and everything on it are affected by FORCES . 2. A force is a PUSH OR A PULL that causes an object to move, STOP , change direction, SPEED up, or slow down. It is measured in units called NEWTONS (N) after Sir Isaac Newton.
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FORCE AND MOTION
1. Earth and everything on it are affected by FORCES. 2. A force is a PUSH OR A PULL that causes an object to move, STOP, change direction, SPEED up, or slow down. It is measured in units called NEWTONS (N) after Sir Isaac Newton.
Look closely at each picture. What would you do with it: push or pull? Drag it behind the green box in which it belongs (but make sure some of the picture sticks out!). Check your answers on the next page.
3. There are three forces on Earth every day that affect motion: friction, MAGNETISM, and gravity.
What force is present in this picture: a push or a pull? In which direction will the object move? Which object will move and why?
4. Friction opposes or acts AGAINST motion. • It occurs when two objects RUB against each other. • The harder the surfaces press together, the MORE friction there will be. • Friction occurs in LIQUIDS and GASES as well as between solids. • Without friction , it would be difficult to SLOW or stop the motion of objects. Video: Friction 3:09
Frictional_Forces_4.ppt • Friction produces HEAT. • In Latin, fricare means “to RUB.” • It depends on the object's SURFACE (rough or smooth) , object's MASS (heavy or light), object’s SHAPE (aerodynamic), surface area of object (big or small) in liquids and gases, and how hard an object is pushed. • Air RESISTANCE is like friction. For example, the size of a parachute's canopy can affect how fast the parachute will touch ground. • Objects with MORE mass will have more friction. Two bricks will be harder to pull than one brick.
What do the top arrows in each picture represent? What do the bottom arrows represent? In the top picture, which block will move faster and why? In the bottom picture, which block will move faster and why?
LUBRICANTS will reduce friction. Examples include water, GREASE, wax, and motor oil. Without lubrication, moving parts of machines would slow down or stop very quickly. • WHEELS or rollers can also reduce friction. Heavier objects can be moved more easily across the floor if on wheels.
Objects that are aerodynamic will allow less friction. Think of rockets and how they are shaped and cyclists and their helmets. They are ROUNDED so they can glide through the air with little resistance.
5. MAGNETISM is the ability of an object to push or pull on another object that has magnetic properties. • Magnetic force acts at a DISTANCE and cannot be SEEN. • Magnets have poles (NORTH AND SOUTH). • Unlike poles (N-S) ATTRACT or pull towards each other.
Like poles (N-N or S-S) REPEL or push away from each other. • Magnetism is greater at the POLES. • The CLOSER the objects, the GREATER the magnetic force.
IRON, nickel, and a few other metals are attracted to magnets. Not all metals will be magnetic. • A magnet produces a magnetic FIELD around itself and affects certain objects. Magnetic force can act without TOUCHING objects. • The needle of a compass moves because of Earth's MAGNETISM. Magnetic_Force_2_PPT.ppt
Where is the force of magnetism the greatest in this picture and how do you know?
6. Gravity affects objects on Earth all the time. • It hold things to the SURFACE of the Earth. • It pulls objects (big or small) TOWARDS each other. • Gravity is WEAKER between smaller objects and larger for objects of greater mass. • The CLOSER objects are to each other, the greater the force of gravity. Video: What is Gravity 1:23 Video: Intro to Forces and Gravity 3:15
Gravitational_Force_3.ppt • The gravity between Earth and anything on it is noticeable because the MASS of Earth is so large. The pull of Earth's gravity makes any object FALL TO THE GROUND. • As the moon goes around Earth, its gravity pulls on Earth causing WATER in the oceans to move towards the moon. This movement is called TIDES. • Earth's gravity also pulls on the MOON and keeps the moon moving around Earth. In the same way, the pull of the SUN keeps Earth moving around the sun.
graph... This means that, wherever you are in the world, "down" is always towards the ground - even though your "down" isn't the same direction as anybody else's.
7. Motion is the change of an object’s POSITION over a period of time. It is described in terms of position, direction, and speed. • Distance is the LENGTH traveled. It is measured in meters (m), kilometers (km), feet (ft), or miles (mi). • Distance from the REFERENCE point changes when the object moves.
7. Motion is the change of an object’s POSITION over a period of time. It is described in terms of position, direction, and speed. • Distance is the LENGTH traveled. It is measured in meters (m), kilometers (km), feet (ft), or miles (mi). • Distance from the REFERENCE point changes when the object moves. • Direction is the PATH that an object moves and can be determined by reading a COMPASS. It can be described using the terms north, SOUTH, east, west, RIGHT, left, FORWARD, toward, UP, down, or with degrees.
Speed is a measure of how FAST an object is moving. To determine speed you must know TIME and distance traveled. • Time is how LONG it takes. It is measured in SECONDS (sec), MINUTES (min), or HOURS (hr). Motion_5.ppt video: Laws of Motion 17:28
8. In order to observe motion, you must first observe or determine an object’s POSITION, or its place or location. • Position can be described using points on a GRID • An object's motion depends on your FRAME of reference (a group of objects from which you can measure a position or motion).
1. What do the arrows represent in this picture? 2. What part of the map shows you direction? 3. What direction is the car on the left traveling? On the right? 4. What do the squares represent on this map?
Position of an object is its LOCATION relative to another object (called the REFERENCE point). • Words that describe position include ABOVE, below, besire, BEHIND, ahead of, as well as the distance from the object. • An object is moving if its position CHANGES. • An object not moving is at REST.
In what direction would you be traveling on a trip from Chicago to St. Louis? How would you know? Which city is the greatest distance from Chicago? What direction would you be traveling if you left Chicago for Des Moines?
9. Forces can be BALANCED or unbalanced. SEVERAL forces can act on an object at the same time. • 10. Balanced forces are EQUAL in size (and strength)and OPPOSITE in direction. • They will not change the object's MOTION or direction. Balanced_and_Unbalanced_Forces_6.ppt
The forces on this pinata are balanced, because it it hanging still.
11. Unbalanced forces occur when one force is GREATER than its opposite force. • Unbalanced forces change the RATE and DIRECTION of the motion of objects. • If the object is AT REST, an unbalanced force will cause it to move in the DIRECTION of the force. • A stronger FORCE (push or pull) will make an object move FASTER.
The object's MOTION will change with unbalanced forces. • They will cause an object to MOVE, stop, speed up, slow down, or CHANGE DIRECTION. • An object will move in the direction of the GREATER force. • If force is applied in the same direction as a moving object, the object will SPEED UP.