Motion Force What is motion Motion a change

Motion & Force

What is motion? • Motion - a change in the position of an object • Motion is all around you! It is a dog walking, a car driving, air circulating, & the Earth revolving around the Sun! • Can you think of any more examples?

Force • Force - a push or a pull on an object • Force can cause objects to start moving, stop moving, or change direction

Push • Push - a force pressed against something to make it move forward, outward, or upward

Pull • Pull - a force that moves something toward or nearer

Push or Pull? • • • Throwing a baseball Picking up a book Rolling a ball to a friend Pedaling a bike Riding a seesaw Jumping off a diving board Shooting a basketball Opening a can of Coke Drinking out of a straw Opening a car door Removing a nail from a wall Dropping a book on the floor

Mass & Distance • Objects with less mass travel faster & go a farther distance. • Objects with more mass travel slower & go a shorter distance.

Speed it up! • Moving items speed up (accelerate) & slow down (decelerate). • The amount that an object accelerates or decelerates is determined by it mass & how much force is pushing or pulling it.

Balanced Forces • Balanced forces do NOT cause objects to move. • Example - Imagine a game of tug of war. If both teams pull the rope with the same amount of force, the rope will not move because the two forces are balanced. • Can you think of any more examples?

Useless Fact • The longest tug of war game took place between Ireland & England during the Tug of War World Championship in 1988. It lasted 24 minutes & 45 seconds!

Unbalanced Forces • Unbalanced forces cause objects to move. • Example- Think back to the game of tug of war. If one team pulls with more force than the other team, the forces are unbalanced. The team that is pulling with more force will win the game. • Can you think of any more examples?

Gravity • Gravity - a force of attraction between two objects • Gravity is a noncontact force because the two objects don’t touch each other.

Hmmm… • Gravity depends on two factors: the mass of the two objects & the distance between them. • Think about this - The Earth is the most “massive” object near us. We are pulled toward the Earth. The Sun is way more massive than the Earth. Why don’t we fly off into space toward the Sun?

Tell how gravity affects the following: • Trapeze swinger • Basketball player • Diver • Hang-glider

Friction • Friction - a force that slows down or stops moving objects • Friction is a contact force. Objects must be touching for friction to occur. • Think about this - If friction did not exist, what would happen?

Tell whether friction is being used or reduced: • • • • Grease a bike chain Butter a cake pan Rub sticks together to start a fire Grate cheese Pedal a bike Oil a door hinge Put lotion on to remove a ring Smooth wood with sandpaper Run wearing rubber-soled shoes Run wearing socks Slide down a snowy hill Slide down a grassy hill Rub your hands together to get warm

Air Resistance • Air Resistance - friction from the air • Things with a larger surface area have more air resistance. • Try this - Drop a paper wad & a flat sheet of paper at the same time. Which one lands first? WHY?

Tell whether each object is using or reducing air resistance: • Racecar • Hang-glider • Kite • Skier

Isaac Newton • Created the Three Laws of Motion

First Law of Motion • An object at rest will remain at rest unless acted on by an unbalanced force. • An object moving in a straight line will continue moving in a straight line unless acted on by an unbalanced force.

First Law of Motion • Seatbelt • Ketchup bottle • Skateboard • Floor rug • Hockey puck

Second Law of Motion • Fancy - Motion depends on an object’s mass & the amount of force acting on it. • Duh! - Moving heavy objects requires more force than moving light objects.

Second Law of Motion • You kick a soccer ball & a brick wall. Which one moves? • Amy weighs 78 lbs. & her dad weighs 187 lbs. They go to the batting cages. Who will hit the ball farther? • Tony & Hose practice blocking tackle dummies at football practice. Tony weighs more. Which dummy will move the most? • A sports car & a delivery truck break down. The drivers need to push them to the side of the road. Which vehicle will get moved first?

Third Law of Motion • For every action there is an equal & opposite reaction.

Third Law of Motion • A girl & a boy are on skates. The girl pushes the boy. What happens? • A frog is sitting on a lily pad. It jumps. What happens? • A man paddles a boat. What happens?