2 Newton’s First Law of Motion Objects in motion tend to stay in motion until something “hits” themObjects at rest tend to stay at rest unless something “hits” themLet’s test it - Use a ball and try for yourself!
3 You may have noticed. . .Things tend to keep on doing whatever they’re doing until something else “hits” them.
4 ForcesWhen you were pushing, pulling, nudging, or blowing on the ball you were causing the “hits” that moved the object.These things, along with other things that change motion, are called forces.
5 Why do they do that? INERTIA An objects tendency to keep doing what it’s doing is its inertia.An object with lots of inertia requires more force to change its motion.An object with less inertia requires less force to change its motion.
6 Now why did the things stop??? A FORCE called FRICTIONYour test objects stop because they “hit” other objects (which could even be air particles). These “hits” cause friction and this causes the object to come to rest.
7 Newton’s Second Law of Motion Mass - measure of an object’s inertia: big inertia=big mass, small inertia=small massA force acting on an object = mass of the object x acceleration of the objectF=maLarger force on small mass=large acceleration
8 Speed is related to this law: Obtain a meter stick, a ball, and a timing device.Start rolling the ball and begin timing when the ball reaches one end of the meter stick and stop timing when it reaches the other end.Record the distance (I meter) and the time.To calculate the speed of the marble, divide the distance traveled by the time it took to cover that distance. That is the object’s speed!
9 Use an equation to find the speed... Speed can be written using ”s” for speed or “r” for rate, or “v” for velocity.Distance traveled can be “d”; time can be represented by “t”s= d/t, r=d/t, v=d/t,Just know what the letters mean!
10 More info related to speed Velocity-tells how fast something is going and its direction (for example 65 mph North)Vectors-arrows that can show velocity, magnitude (size), and direction.Average speed is the what you get from s=d/t.Instantaneous speed is your speed at a given instance in time.Acceleration is a change in velocity (i.e.. Change in direction or speed or both) For example, a car speeding up(which is why they call it an accelerator on the car)Another equation for you: acceleration=change in velocity/time for the changeYour body can detect changes in acceleration.
11 What is Gravity? The earth’s pull (or force) on things Let’s test it. (it is also a force that exists between all objects)Let’s test it.Drop two things.What happened?They should have hit the ground at about the same timeWhen gravity is the only force applied, all objects have the same acceleration
12 Mass vs. Weight Weight: The force that gravity exerts on an object If you change gravity, the weight would also change.Mass: A measure of an object’s inertia--how hard it is to change the motion of an objectIf you change gravity, the mass would stay the same.
13 Can distant objects influence our daily lives? Because of gravity, you have a stronger attraction to things closer to you. You’ll be more attracted to something located on Earth than something located on Jupiter.
14 Are astronauts really weightless when they orbit the Earth? No, because weight is the force of Earth’s gravity and under normal conditions you are not ever totally away from that force.
15 How do other examples of Gravity affect things on Earth? Everything exerts some type of gravitational force on everything else.One example: The gravitational forces between the moon and the waters found on Earth are responsible for the things we call Tides!-