Physics

Motion in a straight line

Distance and displacement

• Distance is a concept familiar to you. 
• When you go from home to school, you have to travel a certain distance. Sometimes, there can be several paths you could use to travel between home and school. Some of them could be shorter and some longer.

• A physical quantity which can be described only by its magnitude is called a scalar quantity
• .eg: speed, mass, time, distance
•  
• A physical quantity which can be described by its magnitude and direction is called a vector quantity
• .eg: displacement, acceleration, velocity, weight
•  

•  Speed

• We frequently hear about accidents caused by vehicles moving at high speeds.
• Due to this reason, there are different regulatory
• speed limits assigned to different roadways. 
• We should obey these speed limits in order to prevent accidents, particularly in highways with high-speed limits.
• What we mean by speed is the rate at which a given distance is traveled.
• In other words, speed is the distance traveled in a unit time.
• speed =distance/time

•  Velocity

  • Because we calculate the speed in terms of distance, we do not consider the direction when we calculate the speed. 
  • Therefore, it must be clear to you by now, that the speed is a scalar quantity. 
  • The velocity however, is defined as the rate of change of the displacement. Therefore, it is a vector quantity that has both a magnitude and a direction.
  • The velocity of an object can be obtained by dividing its displacement by time.
  • Velocity = displacement /time