1. Motion is one of the key topics in physics. Everything in the universe moves. It might only be a small amount of movement and very very slow, but movement does happen. Don’t forget that even if you appear to be standing still, the Earth is moving around the Sun, and the Sun is moving around our galaxy. The movement never stops. Over the years, scientists have discovered several rules or laws that explain motion and the causes of changes in motion. Motion

2. The physics of motion is all about forces. Forces need to act upon an object to get it moving, or to change its motion. A force can be describe as a push or pull of an object. Changes in motion won’t just happen on their own. So how is all of the motion measured? Physicists use some basic terms when they look at motion. How fast an object moves, its speed or Velocity, can be influenced by forces. Speed it Up, Slow it Down

3. Acceleration is a twist on the idea of velocity. Acceleration is a measure of how much the velocity of an object changes in a certain time (usually one second). Velocities could either increase or decrease over time. Mass is another big idea in motion. Mass is the amount of something there is, and is measured in grams (or kilograms). A car has a greater mass than a baseball. In order to really understand motion, you have to think about forces, acceleration, energy, work, and mass.

4. If you were a ball sitting on a field and someone kicked you, a force would have acted on you. As a result, you would go bouncing down the field. There are often many forces at work. If you were standing in one place, you would have many forces acting on you. Those forces would include gravity, the force of air particles hitting your body from all directions, and the force being exerted by the ground. Examples of Force

5. Let’s look at the forces acting on that soccer ball before you kicked it. As it sat there, the force of gravity was keeping it on the ground, while the ground pushed upward, supporting the ball. There may have been small forces trying to push it. Those forces were too small to get it rolling, but they were there. And you never know what was under the ball. Maybe an insect was stuck under the ball trying to push it up. That’s another force to consider. If there is more than one force acting on an object, the forces can be added up if they act in the same direction or subtracted if they act in opposition. Scientists measure forces in units called Newtons.

6. http://studyjams.scholastic.com/studyjams/ jams/science/forces-and-motion/force-and- motion.htm

7. Gravity is a major player in the study of physical science. It is, of course, the force of gravity that causes objects to fall. One object always exerts a force of attraction on another object. This force of attraction is a pull, like the pull of gravity. Why Do Some Objects Fall Faster Than Others?

8. The larger an object is, the greater is the force of its attraction. Consider the fact that the sun, which is much larger than the earth, can, even at 90 million miles away, hold the earth and the other eight planets in orbit. The moon, on the other hand, is much smaller than the earth, and has only about one-sixth of the gravity of earth.

9. It was Italian scientist Galileo who formulated the laws of accelerated motion and free-falling objects. He found that when an object is dropped and falls to the ground it has a falling rate of 9.8 meters per second, squared. You may wonder, then, why feathers float gently in the breeze instead of falling to the ground quickly, like a brick does….

10. Well…..It’s because the air offers much greater resistance to the falling motion of the feather than it does to the brick. The air is actually an upward force of friction, acting against gravity and slowing down the rate at which the feather falls. The brick, on the other hand, can cut right through the air as if it didn’t exist. Galileo discovered that objects that are more dense, or have more mass, fall at a faster rate than less dense objects, due to the air resistance.

11. If a feather and a brick were dropped together in a vacuum— that is, an area from which all air has been removed—they would fall at the same rate, and hit the ground at the same time.

12. http://studyjams.scholastic.com/studyjams/ jams/science/forces-and-motion/fgravity- and-inertia.htm

13. stay Newton’s First Law says that an object at rest tends to stay at rest, and an object in motion tends to stay in motion, with the same direction and speed. Motion (or lack of motion) cannot change without an unbalanced force acting. If nothing is happening to you, and nothing does happen, you will never go anywhere. If you’re going in a specific direction, unless something happens to you, you will always go in that direction. Forever.

14. Why then, do we observe every day objects in motion slowing down and becoming motionless, which appears to happen without an outside force? It’s a force we sometimes cannot see – friction.

15. Here are three types of friction: Sliding friction: ice skating Rolling friction: bowling Fluid friction (air or liquid): air or water resistance What is this unbalanced force that acts on an object in motion?

16. http://studyjams.scholastic.com/studyjams/ jams/science/forces-and- motion/inertia.htm

17. Newtons’s 1 st Law and You Don’t let this be you. Wear seat belts. Because of inertia, objects (including you) resist changes in their motion. When a car going 80 miles per hour is stopped by a brick wall, your body keeps moving at 80 miles per hour.