Speed, Velocity and Acceleration MOTION Speed, Velocity and Acceleration

Motion A change in position measured by distance and time.

Reference Point A place or object used for comparison to determine if something is in motion. So…a fly is sitting on the shoulder of a man sitting in a car. The car is traveling at 60 mph. Is the fly in motion?

Speed The rate at which an object moves. Speed is the distance traveled in a given amount of time Speed = distance time Units= m/sec, km/hr

Calculating Speed Problem: What is the speed of a car that travels 100 miles in 2 hours? Solution: S=d t S=100mi 2hr S=50mph

Velocity The speed and direction of a moving object. Ex. The cheetah’s velocity is 70 mph east

Acceleration The rate at which speed or direction changes. Acceleration occurs anytime an object's speed increases, decreases, or changes direction. Positive acceleration: an object speeds up Negative Acceleration: (or deceleration) an object slows down Zero Acceleration: an object moves at a constant velocity or the object has no motion.

Calculating Acceleration Acceleration= final velocity-initial velocity time

Practice Problem A train traveling at 10m/s slows down to a complete stop in 20s. What is the acceleration of the train? SOLUTION: A= FV-IV T A= 0 m/s-10m/s 20s A= -10m/s A= -.5m/s2

Interpreting Motion Graphs

Key Points A straight line shows constant speed. A curved line shows average speed. A horizontal line shows no motion. Time is on the x-axis, distance is on the y-axis. The steeper the graph, the faster the motion.

Time is always on the x-axis. Distance is always on the y-axis. Distance-Time Graphs Time is always on the x-axis. Distance is always on the y-axis.

No Motion Time is increasing, but distance does NOT change. It is NOT MOVING…NO MOTION…AT REST.

CONSTANT SPEED Time and distance are INCREASING at a constant rate. This graph shows CONSTANT SPEED.

FASTER SPEED A steeper line shows greater distance traveled in a given time. The STEEPER THE LINE, the HIGHER THE SPEED.

ACCELERATION In a given time, the distance the object moves is getting larger, it is ACCELERATING. The curve upward shows an INCREASE in SPEED.

DECELERATION This graph is the same as above, but the curve downward shows DECELERATION or a DECREASE IN SPEED.

Putting it all together