| Your son or daughter has science questions about | | | | acceleration. The strength of the force on an |
| Sir Isaac Newton’s three laws of motion. | | | | object depends upon the object’s mass, or |
| How can you begin to guide your child’s | | | | how much material it contains, and how fast its |
| understanding of these concepts? Without | | | | speed is changing, or its acceleration. An |
| thinking about them, we use Sir Isaac | | | | automobile hitting a wall at the same speed as a |
| Newton’s three laws of motion every day. | | | | roller skate would have more force, since the car |
| Newton’s first law explains why it is harder to | | | | has more mass. A unit of measurement for force |
| stop a moving car than a roller skate. | | | | is the Newton, abbreviated N, named after Sir |
| Newton’s second law algebraically relates the | | | | Isaac Newton. One Newton, or one N, is the force |
| force on an object, its mass, and its | | | | needed to move a mass of one kilogram one |
| acceleration. Newton’s third law concerns | | | | meter per second in a second. Or algebraically, 1 N |
| how forces act upon objects. By relating every | | | | = 1 kg * m/ s2. A Newton of force is a small |
| day experiences, you can help your child | | | | amount. A person weighing 110 pounds exerts a |
| understand Sir Isaac Newton’s three laws of | | | | force of 50 Newtons on Earth. |
| motion. | | | | 3. Newton’s third law of motion is more |
| 1. Newton’s first law of motion is also known | | | | commonly called action reaction. For every |
| as the law of inertia. The term, inertia, derives | | | | action in one direction, there is an equal and |
| from the Greek, inert, or not moving. | | | | opposite reaction in the opposite direction; even if |
| Newton’s first law states that any object will | | | | the object does not move. Forces always act in |
| remain stationary or will continue to move in a | | | | pairs, even if the object remains still. While sitting |
| straight line unless it is acted upon by an external, | | | | in a chair, you provide a force on the chair acting |
| unbalanced force. A force is a push or pull on an | | | | down towards the floor. At the same time, the |
| object. Inertia is a measure of the mass of an | | | | chair provides an equal and opposite upward force |
| object. An automobile has more inertia than a | | | | on you. If this were not the case, you would be |
| roller skate. While you are traveling in a moving | | | | sitting upon the floor instead. While you walk, for |
| car, you are moving in the same direction and | | | | each step that you take your foot pushes against |
| with the same speed as the car. If the car | | | | the floor. As you push, or provide a force, |
| suddenly comes to a stop, you will still be moving | | | | against the floor, the floor also pushes against |
| in the original direction, through the windshield if | | | | your foot, propelling you forward. If you try to |
| you do not use a seatbelt or airbag. The | | | | walk across sheer ice, you must adjust your |
| seatbelt keeps you in one position relative to the | | | | steps, since the ice does not provide the same |
| car’s motion, keeping your body against the | | | | force as the floor. |
| seat. Inertia also explains why you lean towards | | | | By using every day examples, you can help your |
| the opposite direction as the car moves around a | | | | children understand Sir Isaac Newton’s three |
| steep curve. If the car turns right, you lean | | | | laws of motion. The law of inertia, or |
| towards the left; if the car turns left, you lean | | | | Newton’s first law of motion, describes how |
| towards the right. Again, your body continues to | | | | a stationary object begins to move or how the |
| move in a straight line during the turn, as it did | | | | motion of an object changes. Newton’s |
| before the turn. | | | | second law of motion algebraically relates an |
| 2. Any time you want to change the speed or | | | | object’s mass and acceleration to the amount |
| direction of an object, you need to use the | | | | of force involved to cause motion. Finally, |
| appropriate force. Newton’s second law of | | | | Newton’s third law of motion involves the |
| motion relates the concepts of mass, force, and | | | | fact that forces on an object always act in |
| acceleration. In science, acceleration is the change | | | | opposing pairs, whether or not the forces cause |
| in speed or direction of a moving object. Force on | | | | motion. |
| an object is equal to its mass multiplied by its | | | | |