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Motion and Design Notes Miss Calfe Name ___________________________________ I. Force – a push or a pull Balanced forces: two equal forces pushing or pulling in opposite directions. Example: our K’Nex car didn’t move when there were only 2 small washers because the forces were balanced. Unbalanced forces: two forces pushing or pulling in opposite directions with one force stronger than the other. Example: our K’Nex car moved when we added one large washer to our paper clip because the force of gravity was the stronger force. II. First Law of Motion An object in motion will want to stay in motion, and an object at rest will want to stay at rest. A force is needed to get an object moving, stop an object, or change direction. Inertia – a property that states an object wants to keep moving or stay still, and that you need a force to change what something is doing. Examples: Our K’nex car stayed at rest when there were no washers on the paper clip because it was already at rest and there was no force to change that. Our K’nex car kept moving even after the washers hit the floor because it was already in motion. Motion and Design Notes III. Miss Calfe Second Law of Motion The heavier an object is, the more force you need to keep it moving, stop it, or get it to go faster. Acceleration – to go faster Force = mass x acceleration (F = MA) Examples: When we added 2 blocks to our car and kept the washers the same, it move slower because we added mass. To make our car go faster with 2 blocks, we would need more washers (force). IV. Types of Energy Kinetic Energy – the energy of motion Examples When we wind the rubber band around our car’s axle and let the axle go, the wheels begin to spin. At this point, we would call the energy kinetic because the car is moving. Potential Energy – stored energy Examples When we wind the rubber band around the axle, we are storing energy. This is called potential energy because we have stored the energy in the rubber band so the car as the potential to move, but its not moving yet. Motion and Design Notes Miss Calfe II. Friction – the force that opposes motion Air resistance – friction created when air hits a vehicle. Drag – another name for air resistance. Aerodynamic – designs that get rid of or decrease air resistance. ADD FRICTION Tires (+) Cleats (+) Chalk on hands (gymnastics, softball) (+) Tan connectors on the outside (-) Propeller hitting the vehicle while it spins (-) REDUCE FRICTION Tan connectors on the inside (+) Crossbars (+) Wax on skis (+) No tires (-) II. Third Law of Motion – every action has an equal and opposite reaction Examples: When your propeller spins, it pushes air behind it. In an equal and opposite reaction, the air pushes back on the propeller, causing your car to move forward. Soccer ball: when you kick a soccer ball, the ball pushes back on your foot with an equal amount of force. This is why you feel the ball when you kick it. Because the ball has way less mass than you, the force is strong enough to make the ball move, but not you. III. Types of Energy Potential energy – stored energy Kinetic energy – energy of motion POTENTIAL ENERGY Winding the rubber band around the axle KINETIC ENERGY Letting go of the axle/rubber band and the axle spins