Motion Test - 7

Acceleration is a vector quantity.

Since retardation and force are related to acceleration.Therefore,they are vector quantities.

When a body moves from one position to another,the shortest (straight line) distance between the initial position and final position of the body is known as its displacement. Its a vector quantity.

Displacement can be zero,less than the magnitude of distance but can never be more than the magnitude of distance covered.

A body travelling with unifrom speed travels equal distances in equal intervals of time.Hence,both the average speed and instantaneous speed are same.
Average speed is total distance travelled divided by total time taken by object for cover up to that ditance. Average velocity is total displacemet of object divided by total time taken by object to cover up that distance.
So, Statement A is true and Statement B is false.

The device used to measure the instantaneous speed of vehicle is speedometer. The speedometer of a car reveals information about the instantaneous speed of your car. It shows your speed at a particular instant in time.

If a body covers equal distance in equal intervals of time then it is said to be moving at uniform speed. Mathematically speed is defined as v =  S/t , here v is speed of object, S is the distance covered and t is time taken.

When the speed of a body changes in an irregular manner, the speed-time graph of the body is a curved line. The distance traveled by the body is given by the area between the speed-time curve and the time axis.  For uniform speed graph is straight line. For non-uniform speed graph is curved line. For Increasing speed graph  Straight line sloping upwards. For decreasing speed graph Straight line sloping downwards.
When velocity – time graph is plotted for an object moving with uniform acceleration, the slope of the graph is a straight line.
So, statement A is true and B is false.

The speed of train = 120 m /6 = 20 m/s.

Time taken to cross a 50 m long bridge = (120 m + 50 m)/20 = 170/20 = 8.5 second.

1) Distance travelled per unit time is called speed. SI unit for speed is m/s. Speed  = Distance travelled / Time take
2) Displacement per unit time is known as velocity. It is nothing but speed of an object in a definite direction. Velocity = Displacement / Time taken​

3) Rate of change of velocity with time is known as acceleration. SI unit of acceleration is m/s². Acceleration = Change in velocity / Time taken
4) The ratio of total distance travelled to the total time taken by the body gives its average speed.  Average speed =  total distance covred / total time taken​

Uniform Motion means Body covers equal distance in equal time interval.
A satellite goes around the earth in a circular orbit with constant speed and covers equal distances in equal time intervals.
The arms of the clock covers equal distance in every hour.
Moon revolves around the earth and takes equal time for every revolution.
The motion of car in a busy road is not example of uniform motion.