Matter in Motion Chapter 1 Page 3
Measuring motion Section 1
Measuring Motion An objects change in position over time when compared with a reference point
Motion is relative If you are in a car that is going at the same speed, the other car will not by moving with respect to you. But both cars are moving with respect to the ground.
Reference point Any object that will appear to stay in place Moving objects can be used as reference points
Point of Reference cont In talking about motion, it is important to indicate your point of reference. In the case of moving automobiles, it is usually assumed the speed is with respect to the ground. But there are situations where the speed or velocity may be with respect to another object or an observer.
Example For example, suppose a car was traveling at 60 miles per hour (mph) and hit another car, but there was hardly a dent. The reason is that the second car was traveling in the same direction at 59 mph, so the car was going only 1 mph with respect to the second car when it hit it.
Sun looks like it is moving in the sky The sun appears to move across the sky, when the earth is actually spinning and causing that apparent motion. Usually, we consider motion with respect to the ground or the Earth. Within the Universe there is no real fixed point. The basis for Einstein's Theory of Relativity is that all motion is relative to what you define as a fixed point.
Speed Depends on distance and time Speed the rate at which an object moves SI unit is meters/seconds (m/s)
Average Speed Objects do not travel at constant speed therefore we calculate average speed Average Speed = Total Distance Total time
Calculating Average Speed
Answers
Practice
Find the average
Practice
Steps
Practice
Answers
Velocity The speed of objects in a particular direction
Velocity The final component in explaining an object's velocity is including a relative direction. For example, a car that travels 100 meters in 10 seconds, in the westerly direction, would have a velocity of 10 m/s west.
Acceleration: The rate at which velocity changes measured by taking the change in velocity of an object divided by the time is took to change that velocity:
Acceleration For example, if an object speeds up from a velocity of 240 meters/second to 560 meters/second in a time period of 10 seconds, the acceleration is (560 - 240)/10 = 320/10 = 32 m/s/s or 32 m/s².
Practice Problems Math Break Page 5 Page 9
Graphing
The Speed a Car travels
Section 2 Terms to learn: force, net force, newton What is Force Section 2 Terms to learn: force, net force, newton
Force Push or pull
Determining the Net Force Net force: The sum of all the forces which act upon an object
Vectors
Unbalanced = Motion
Balanced = No Motion
Friction Section 3
Friction Any force that opposes motion b/t two surfaces that are touching
Sliding Friction Very effective a opposing force Lot of force must be exert to overcome
Rolling Friction A rolling wheel requires a certain amount of friction so that the point of contact of the wheel with the surface will not slip.
Fluid Friction Friction forces formed b/t liquids and another surface Streamlining reduces fluid friction
Friction = Force Applied= No Motion Static Friction The force of friction that is equal to force applied Friction = Force Applied= No Motion
Ways to change Friction Reduce Lubrication Streamlining Increase Add texture Add force
Gravity: A force of Attraction Section 4
Gravity A force of attraction b/t object due to its mass
Newton’s Idea Unbalanced forces caused an apple to fall from a tree He realized the two forces are one gravity
Law of Universal Gravitation All objects in in the universe attract each other through gravitational force
Forces in action Mass Weight How much matter it contains. It is measured in grams (g) or kilograms (kg) but is NOT a force. Weight The force caused by gravity pulling down on the mass of an object. It is measured in Newtons (N).
Size of Force Depends Mass Distance Larger the mass the greater the force of gravity Distance Closer the distance the greater the force of gravity