Motion, Speed, and Velocity Physics Motion, Speed, and Velocity

Standards Covered Explain the relationship among distance, time, direction, and the velocity of an object Use the formula v=d/t to solve problems related to average speed or velocity Represent linear motion of objects on distance – time graphs

Motion When an object changes its position, motion has occurred. Distance- How far an object has moved. Displacement- How far an object has moved in relation to its starting point. Consider direction Example: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?

Reference Point A place or object used to determine if an object is in motion or moving Using trees on a moving train to determine train is moving

Measuring Distance All systems of weights and measures, metric and non-metric, are linked through a network of international agreements supporting the International System of Units. The International System is called the SI the meter for distance, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the mole for amount of substance

Speed S=D/T

Problems A bug crawled 25.0 cm in 5.0 seconds. Its average speed was ______. S=d/t S= 25cm/5 sec S= 5cm/sec How far was a turtle able to travel In 2.5 seconds at speed of 25m/s? D=ST

Speed- Distance an object travels per unit of time Relationships between speed, distance, and time: Speed = Distance/ Time = d/ t Constant Speed- speed does not change over time Average Speed- speed of motion when speed is changing Avg Speed = Total Distance/ Total Time Instantaneous Speed- speed at any given moment in time (speedometer)

Graphing Motion Graph distance on the y-axis and time on the x-axis Slope = rise = distance = speed run time

Distance - Time Graph If something is not moving, a horizontal line is drawn. If something starts out slow and then speeds up, its change in speed can look like this.

Learning Checkpoint This graph shows several stages of motion: Stage 1: 100 m in 10 s Stage 2: 50 m in 10 s Stage 3: 150 m in 20 s Calculate the speed as indicated by each of the colors. Calculate the average speed. What is the total distance? What is the displacement?

Solution Stage 1: S= d/ t 100 m/ 10 s= 10 m/s Stage 2: S= d/t Ave Speed= Tot d/ Tot t 300 m/ 40 s= 7.5 m/s Distance = 300 meters Displacement = 0 meters

Velocity The speed and direction of an object’s motion. 88 km / hr southwest

Velocity Velocity is the rate of motion in a specific direction. I'm going that-a-way at 30 kilometers per hour. My velocity is 30 kilometers per hour that-a-way.

Velocity When velocity is changing, (change in speed, or direction) the word acceleration is used. You speed up if the acceleration and velocity point in the same direction. You slow down (also referred to as decelerating) if the acceleration and velocity point in opposite directions.

Velocity

Acceleration Acceleration is a measure of how much the velocity of an object changes in a certain time. Final Speed - Initial Speed time

REVIEW: Does the term accelerating only mean "speeding up"? No it refers to any change in speed or direction (velocity). Examples: · a car speeding up as it moves in the same direction · a car slows down as its speed decreases · a car changes the direction in which it is moving by some angle but speed does not change.