﻿ Define velocity. from Physics Motion in Straight Line Class 11 CBSE
Define velocity.

Velocity is defined as the time rate of change of displacement of the object. It is also defined as the speed of an object in a given direction.
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On a two-lane road, car A is travelling with a speed of 36 km h-1. Two cars B and C approach car A in opposite directions with a speed of 54 km h-1 each. At a certain instant, when the distance AB is equal to AC, both being 1 km, B decides to overtake A before C does. What minimum acceleration of car B is required to avoid an accident ? 228 Views

A jet airplane travelling at the speed of 500 km h–1 ejects its products of combustion at the speed of 1500 km h–1 relative to the jet plane. What is the speed of the latter with respect to an observer on the ground ? Negative sign implies that the direction of its products of combustion is opposite to the direction of motion of the jet airplane.
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A car moving along a straight highway with speed of 126 km h–1 is brought to a stop within a distance of 200 m. What is the retardation of the car (assumed uniform), and how long does it take for the car to stop. 175 Views

Two trains A and B of length 400 m each are moving on two parallel tracks with a uniform speed of 72 km h–1 in the same direction, with A ahead of B. The driver of B decides to overtake A and accelerates by 1 m s–2. If after 50 s, the guard of B just brushes past the driver of A, what was the original distance between them ?

In case of train A:

Initial velocity, u = 72 km/h = 20 m/s

Time, t = 50 s

Since the train is moving with uniform velocity,

Acceleration, aI = 0

Now, using second equation of motion,

Distance covered by train A is given by, For train B,

Initial velocity, uB72 km/h = 20 m/s

Acceleration, a = 1 m/s

Time, t = 50 s

Now, using second equation of motion,

Distance travelled by second train B is, Length of both trains = 2 Therefore, the original distance between the driver of train A and the guard of train B = 2250 - 1000 - 800
= 450m.

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A drunkard walking in a narrow lane takes 5 steps forward and 3 steps backward, followed again by 5 steps forward and 3 steps backward, and so on. Each step is 1 m long and requires 1 s. Plot the x-t graph of his motion. Determine graphically and otherwise how long the drunkard takes to fall in a pit 13 m away from the start.  167 Views