Category: elementary

By Lorie Moffat

Your son or daughter has science questions about Sir Isaac Newton’s three laws of motion. How can you begin to guide your child’s understanding of these concepts? Without thinking about them, we use Sir Isaac Newton’s three laws of motion every day. Newton’s first law explains why it is harder to stop a moving car than a roller skate. Newton’s second law algebraically relates the force on an object, its mass, and its acceleration. Newton’s third law concerns how forces act upon objects. By relating every day experiences, you can help your child understand Sir Isaac Newton’s three laws of motion.

Newton’s first law of motion is also known as the law of inertia. The term, inertia, derives from the Greek, inert, or not moving. Newton’s first law states that any object will remain stationary or will continue to move in a straight line unless it is acted upon by an external, unbalanced force. A force is a push or pull on an object. Inertia is a measure of the mass of an object. An automobile has more inertia than a roller skate. While you are traveling in a moving car, you are moving in the same direction and with the same speed as the car. If the car suddenly comes to a stop, you will still be moving in the original direction, through the windshield if you do not use a seatbelt or airbag. The seatbelt keeps you in one position relative to the car’s motion, keeping your body against the seat. Inertia also explains why you lean towards the opposite direction as the car moves around a steep curve. If the car turns right, you lean towards the left; if the car turns left, you lean towards the right. Again, your body continues to move in a straight line during the turn, as it did before the turn.

Any time you want to change the speed or direction of an object, you need to use the appropriate force. Newton’s second law of motion relates the concepts of mass, force, and acceleration. In science, acceleration is the change in speed or direction of a moving object. Force on an object is equal to its mass multiplied by its acceleration. The strength of the force on an object depends upon the object’s mass, or how much material it contains, and how fast its speed is changing, or its acceleration. An automobile hitting a wall at the same speed as a roller skate would have more force, since the car has more mass. A unit of measurement for force is the Newton, abbreviated N, named after Sir Isaac Newton. One Newton, or one N, is the force needed to move a mass of one kilogram one meter per second in a second. Or algebraically,

1 N  =

1 kg

m s2

A Newton of force is a small amount. A person weighing 110 pounds exerts a force of 50 Newtons on Earth.

Newton’s third law of motion is more commonly called action reaction. For every action in one direction, there is an equal and opposite reaction in the opposite direction; even if the object does not move. Forces always act in pairs, even if the object remains still. While sitting in a chair, you provide a force on the chair acting down towards the floor. At the same time, the chair provides an equal and opposite upward force on you. If this were not the case, you would be sitting upon the floor instead. While you walk, for each step that you take your foot pushes against the floor. As you push, or provide a force, against the floor, the floor also pushes against your foot, propelling you forward. If you try to walk across sheer ice, you must adjust your steps, since the ice does not provide the same force as the floor.

By using every day examples, you can help your children understand Sir Isaac Newton’s three laws of motion. The law of inertia, or Newton’s first law of motion, describes how a stationary object begins to move or how the motion of an object changes. Newton’s second law of motion algebraically relates an object’s mass and acceleration to the amount of force involved to cause motion. Finally, Newton’s third law of motion involves the fact that forces on an object always act in opposing pairs, whether or not the forces cause motion.

Lorie Moffat has 20 years of teaching experience in both public school classroom and science museum settings.

Source: http://www.homeschool-articles.com/helping-kids-understand-sir-isaac-newton%e2%80%99s-three-laws-of-motion/

By Lorie Moffat

Your son or daughter has questions about the different kinds of potential energy, or energy that is stored. It can be quite confusing since some examples are not stationary on a molecular level. Some types are actually potential and kinetic (energy of motion) simultaneously, like heat or chemical. You can explain the differences between the six kinds of potential energy to your child using common examples.

Potential energy, or the energy of position, is stored energy. That is, it has the capacity to do work or to move something in a scientific sense. There are many types of potential energy including gravitational potential, electrical, chemical, thermal, magnetic, and elastic.

• Six Kinds of Potential Energy #1 – When an object such as a ball is on the slope of a hill, it has gravitational potential energy based upon its height from the bottom of the hill, its mass, and the gravitational constant, g, which on Earth is 9.8m/s2. The gravitational constant is a form of acceleration. The higher an object is above the Earth’s surface, the more it will accelerate as it falls until it reaches terminal velocity (or the fastest speed at which it will fall). If a ball with the mass of 10 kilograms is 100 meters above the Earth’s surface, its gravitational potential energy will be the product of mass, gravitational constant, and height; or (10 kg) (9.8 m/s2) (100m), which is 9800 kgm2/s2 or 9800 Newton-meters or 9800 Joules. A Joule, which rhymes with rule, is the metric unit for energy. A ball’s potential energy changes to kinetic as it rolls or falls downhill.

• Six Kinds of Potential Energy #2 – Electrical energy is stored in a battery in the chemical elements the battery contains. One battery terminal has an element that allows electrons to flow from it while the other terminal has an element that readily accepts electrons. A battery eventually stops working because the chemicals get used up. Static electricity involves objects like a balloon or the family’s pet cat that have extra electrons, especially in dry weather. If you rub a balloon on your hair and stick it to the wall, that’s using static electricity. When you pet the cat on a dry day, you may hear a crackling sound or see tiny sparks which is also static electricity.

• Six Kinds of Potential Energy #3 – Chemical energy is trapped in chemical bonds. It is the component of the energy that can be released when molecules interact during a chemical reaction. It includes fossil fuels like coal, oil, natural gas and wood. Chemicals are composed of molecules, which are composed of atoms, which are composed of protons, neutrons, and electrons for practical purposes. Electrons are in constant motion circling the protons and neutrons in the nucleus. The motion of electrons is involved with chemical bonds creating molecules. During a chemical reaction this energy gets stored. Our cells need the chemical energy stored in the foods that we eat in order to function properly. Digestion is a slow process that breaks down the food we eat, releasing energy for the body’s use. The energy from foods becomes heat, carbon dioxide and water. Food packages list the number of Calories in the product. One Calorie of food energy is 4180 Joules.

• Six Kinds of Potential Energy #4 – Thermal or heat energy is in all matter. Even something that feels cold like an ice cube still has heat. The molecules of all matter moves even as part of a solid. As long as the temperature of a material is above absolute zero, which is -459 degrees Fahrenheit, it has heat. This type of heat is still considered stored since it does not involve motion that we can see.

• Six Kinds of Potential Energy #5 – Magnetic energy is also related to the atoms in an object. A magnet has extremely large groups of atoms lined up, in which one side of the group becomes the north pole of the magnet and the other side becomes the south pole. The magnetic field, or the space around a magnet where the magnetic force is exerted, is created by spinning and orbiting electrons. Most materials are not magnetic because the atoms’ magnetic fields do not line up. Iron atoms produce the strongest magnetic field therefore lots of magnets contain iron. Magnets are in electric motors and exert forces that affect the electrical current in wires. This led to the development of electric power, radio, and television.

• Six Kinds of Potential Energy #6 – Elastic energy is the internal energy of a fluid or a solid that can be converted into mechanical energy to do work. A bouncing ball, a spring, a trampoline’s webbing, and a hydraulic piston all have elastic energy. The ball, spring, and trampoline all are solids that can store energy. The piston contains either compressed air or another fluid such as the brake fluid in automobile brakes that store energy.

By using common the examples above, you can easily explain the different kinds of potential energy to your children.

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Lorie Moffat has 20 years of teaching experience in both public school classroom and science museum settings. Contact her about special summer online tutoring packages.
Source: http://www.homeschool-articles.com/teaching-children-about-the-six-kinds-of-potential-energy/