Transcript Forces and Motion
Forces and Motion Force • A force is a push or pull on an object. (measured in Newtons) • Sets an object in motion, changes its speed, or changes its direction. – Gravity – Friction Motion • Motion is the change in the position of an object. • To observe motion, a reference point is used. – A stationary object which can be used to measure motion. http://www.youtube.com/watch?v=ExjbcUmmc Rg Speed • Speed is the distance an object moves in a certain time period. • Velocity is the speed of an object IN A GIVEN DIRECTION. • To solve for speed, take the distance and divide the time. Solving for Speed • If Mr. Cleland runs 10 meters in 2 seconds, what is his speed? – 5 m/s • If Mr. Parke throws a baseball 12 meters in 4 seconds, what is the speed of the ball? – 3 m/s • Time=distance/speed. • Distance=time x speed. • If Mr. Whiting runs 15 meters at a speed of 3 m/s, what how long did it take him? – 5 seconds. • If Ms. Hetrick runs for 5 seconds at a speed of 4 m/s, how far does she go? – 20 meters. Graphing Motion • You can show the motion of an object on a line graph where you plot distance vs time. • X axis is the time. • Y axis is the distance. • The slope of two points on a line will tell you the speed. • Different slopes tell the different speeds of an object. Acceleration • The rate at which velocity changes. – If speed changes, direction changes, or both. • Acceleration is final speed – starting speed then dividing by time. • If Mrs. Greiser is driving her Mercedes and accelerates from 10 m/s to 16 m/s in 3 seconds, what is her acceleration? – 2 m/s^2 • If Mr. Stevenson is driving his Ford on the freeway at 66m/s and hits a pothole, slowing the vehicle to 44m/s in 11 seconds, what is his deceleration or negative acceleration? – -2m/s^2 • If a plane increases speed from 300 m/s to 450 m/s in 5 s, what is its acceleration? • A rocket is launched and reaches the speed of 7,000 m/s in 15s. What is its acceleration? • Mr. C drives 200 km at a speed of 20 km/hr. How long did it take him? • Mr. C drives 200 km at a speed of 20 km/hr. How long did it take him? • Mrs. Swafford accelerates from 200 m/s to 350 m/s in 5 seconds. What is her rate of acceleration?