motion- speed and velocity

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By: flowersun (94 month(s) ago)

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Mechanics:

Mechanics

MECHANICS:

MECHANICS the sub branch of classical physics that is concerned with the forces acting on bodies , whether at rest or in motion. is divided into statics, kinematics and dynamics

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STATICS - focuses on the way in which forces combine with each other so as to produce equilibrium .

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KINEMATICS - focuses on the motion of a body without regard to the cause of that motion

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DYNAMICS - focuses on the way in which forces produces motion.

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MOTION defined as the movement of an object exhibited by a change in position

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Motion or Movement is a Change In Position 10 ft. Position A Position B

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There are many ways of describing motion: 1. Rectilinear motion- the motion of an object traveling at a straight path. 2. Curvilinear motion- an object traveling in a curved path 3. Angular motion - an object traveling at certain angles

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MOTION IS RELATIVE it may be described by specifying how far something has traveled in changing position and time. a reference frame is a physical entity such as the earth’s surface, the deck of a ship or a moving vehicle to which the position and the motion of an object is relative.

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DISTANCE AND DISPLACEMENT DISTANCE - the total path length traversed by an object moving from one location to another - a scalar quantity which has only magnitude.

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2. DISPLACEMENT- refers to the straight line distance between the starting and end points. - a vector quantity which has both magnitude and direction

Distance and Displacement:

Distance and Displacement START FINISH Need to distinguish how long we traveled from how far away (and in what direction) we traveled.

2 Displacement and distance:

your home your school A displacement has Size = length of this arrow displacement from home to school 2 Displacement and distance To go to school from home... size & direction .

2 Displacement and distance:

Distance = length of path you travelled (  size of displacement ) l 1 l 2 l 3 2 Displacement and distance To go to school from home... your home your school = l 1 + l 2 + l 3

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Suppose we have two towns A and B 10 km apart on either side of a hill.  They are joined by a railway line that is straight, and goes through the hill in a tunnel.  The road goes round the hill and the total journey distance is 25 km.

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So the distance is 25 km.  The displacement (the straight-line distance in a particular direction) between A and B is 10 km due East.

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If we go from A to B and back again, the distance is 50 km, but the displacement is 0.

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SAMPLE PROBLEM: On his way to school, Jed traveled 100 m North, 300 m East, 100 m North, 100 m East , 100 m North. a. Find the total distance traveled by Jed. b. Determine the displacement made by Jed.

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SPEED AND VELOCITY: SPEED- a scalar quantity which measures how fast something is moving.

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SPEED-the rate at which distance is covered at a given time

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average speed- defined as the total distance traveled divided by the time it took to travel the distance.

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the speed of a body at any instant. Instantaneous speed

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VELOCITY- a vector quantity that represents a rate of change of displacement.

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Problems: 1. Rachel watches a thunderstorm from her window. She sees the flash of lightning bolt and begins counting the seconds until she hears the clap of thunder 5.0 seconds later .

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Assume that the speed of sound in air is 340 m/s and light was seen instantaneously. How far away was the lightning bolt?

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2. A car starts from rest and attains a speed of 50m/s in 15 seconds.

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How far has the car traveled in 15 seconds?

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A car traveled at 88 km/hr for 5 hours. How far did it travel?

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Justin walks 5 km/hr. How long did it take him to travel 15 km?

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6. A car travels a distance of 40 km from Manila to a town in Laguna. What is its average speed (in km/hr) if traveling time is from 7:00 A.M. to 7:30 A.M.? its average velocity (km/hr).

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Suppose that after a business talk with a friend , the driver of the car drives straight back to Manila from 11:55 A.M. to 12:20P.M.What was the car,s average speed (km/hr) during the roundtrip? its average velocity (km/hr)

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