Chapter 9 Motion and Machines

Chapter 9Motion and Machines 6th Grade Science Shiloh Christian School

Motion and Machines • Energy – the ability to do work • Potential Energy – stored energy • Kinetic Energy – energy due to motion • Mechanical Energy – the ability to make something move; both potential and kinetic energy are forms of mechanical energy

Motion and MachinesMOTION • Motion – the change of an object’s position • Reference Point – a fixed, unmoving object or location; something that remains still

Motion and MachinesMOTION – Distance and Speed • Distance – determined by measuring an object’s position at different times • Distance = Speed x Time • Speed – determined by dividing the distance an object travels by the time it takes the object to travel that distance; measured in length units per time such as m/s, km/h or mi/h; also called rate • Speed – Distance ÷ Time • Instantaneous Speed – the speed of an object at any one moment • Average Speed – the average speed an object travels during an entire trip

Motion and MachinesMOTION – Velocity and Acceleration • Velocity – the distance an object moves over a given amount of time in a certain direction • A car traveling around a curve changes velocity even if its speedometer shows a constant speed • Acceleration – change in velocity during a period of time • Acceleration occurs whenever an object speeds up, slows down, or changes direction • Force – a push or a pull; measure in Newtons • Friction – a force that keeps objects from moving against other objects

Motion and MachinesMOTION – Momentum • Momentum – determined or affected by the mass and velocity of an object • The greater the mass (the quantity of matter in an object), the greater the momentum

Motion and MachinesLAWS of MOTION • Galileo Galilei – discovered that a moving object does not come to rest unless an outside force acts on the object. • Sir Isaac Newton – continued Galileo's study of how and why things move; formulated the three laws of motion

Motion and MachinesLAWS of MOTION – First Law of Motion • First Law of Motion – an object tends to stay at the same velocity unless another force causes it to change • An object at rest (zero velocity) tends to stay at rest • An object traveling in a straight line at a constant speed tends to keep moving that way. • Inertia – the resistance to a change in motion

Motion and MachinesLAWS of MOTION – First Law of Motion • Mass – the amount of matter in an object • Weight – the gravitational force on an object; a measure of force • Two forces that work against a moving object • Gravity – the pull of one object on another • Greater mass = stronger gravitational pull; the earth has more mass than anything on it so it pulls objects toward itself • Friction • Lubricants such as wax (skiing) and oil (machine parts) reduce friction on parts that rub together

Motion and MachinesLAWS of MOTION – Second Law of Motion • Second Law of Motion – force is equal to an object’s mass and the acceleration of the object. • Force = Mass x Acceleration (f=ma) • PRINCIPLES of this formula • The greater the mass of the object, the greater the force needed to move it • The greater the force exerted on the object, the greater its acceleration will be • The greater the acceleration, the greater the force exerted on an object

Motion and MachinesLAWS of MOTION – Third Law of Motion • Third Law of Motion – when one object exerts a force on another object, the second object reacts by exerting an equal force back on the first object • Forces work in pairs • “The law of action and reaction” • How do we react to the world around us? • We can control our reactions through the help of the Holy Spirit. • We should respond to the words and actions of others in the same way Christ dealt with harsh words, beating and death… that is with love and compassion towards others.

Motion and MachinesMACHINES - Work • Work – a force acting on something as it moves a certain distance • Force (Newtons) x distance (meters) = work (joules) • Work = force x distance • Newtons – (N) the unit used to measure force • How many Newtons of gravitational force are being exerted on an object • Joule – the unit used to measure work

Motion and MachinesMACHINES – Simple Machines • Machine – any object that makes work easier • Makes the work easier by strengthening the force used to do the work or by changing the direction of the applied force • Effort Force – the force (push or pull) applied to a simple machine • Resistance Force – the force (push or pull) that works against the effort • Six Simple Machines – lever, pulley, wheel and axle, inclined plane, wedge, and screw

Motion and MachinesMACHINES – Simple Machines - Lever • Lever – any bar that turns on a point, such as a seesaw, wheelbarrow, or broom • Fulcrum – the spot where the bar turns or pivots • Classification of levers – depends on where the effort and resistance are located in relation to the fulcrum • First-Class Lever – the fulcrum is located between the effort and the resistance; seesaw, crowbar • Second-Class Lever – the resistance is between the effort and the fulcrum; door, wheelbarrow • Third-Class Lever – the effort is between the resistance and the fulcrum; broom, fishing pole

Motion and MachinesMACHINES – Simple Machines – Pulleys • Pulley – a grooved wheel with a chain or rope wrapped in the groove • Pulleys are used to raise and lower things • Pulleys make work easier by changing the direction of the force or by reducing the amount of force needed to move an object

Motion and MachinesMACHINES – Simple Machines - Pulleys • Fixed Pulley – changes the direction of force without reducing the amount of work • Attached to something; flagpole • Moveable Pulley – reduces the amount of force needed to move an object or produce a gain in force • Block and Tackle – a combination of moveable and fixed pulleys • Fixed pulleys changes the direction of force while the moveable pulleys produce a gain in force; sails on sailboats, construction cranes • Mechanical advantage – the decrease in effort that is needed to move an object

Motion and MachinesMACHINES – Simple Machines – Wheel and Axle • Wheel and Axle – consists of a wheel and a rod, or axle, running through the wheel • Two ways work is done • Apply force to the axle to make the wheel move a greater distance • Turn the wheel to make the axle turn with greater force • Gear – a wheel and axle that has tooth-like projections around the wheel • Examples – screwdriver, turbine, gear, doorknob

Motion and MachinesMACHINES – Simple Machines – Inclined Plane • Inclined Plane – a flat, slanted surface, such as a ramp • A more gradual slope requires less force to move an object, making the work easier • However, it has a longer distance to travel

Motion and MachinesMACHINES – Simple Machines – Wedge • Wedge – two inclined planes placed back-to-back • Splits or lifts objects • Long, thin wedges are better than short, fat wedges • Friction keeps wedges in place and prevents them from sliding

Motion and MachinesMACHINES – Simple Machines – Screw • Screw – an inclined plane wound around a cylinder or a cone • Threads – ridges in the screw • As they are turned, they cut into a material and hold the screw in place • Examples – jar lid, winding mountain roads

Motion and MachinesMACHINES – Compound Machines • Compound machines – combine two or more simple machines to make work even easier • Examples • Scissors • Blades – two levers • Cutting edges – wedges • Screw and screwdriver • Screw – simple machine • Screwdriver – wheel and axle

Chapter 9 Motion and Machines