Zigya Logo

Chapter Chosen

Motion in Straight Line

Book Chosen

Physics Part I

Subject Chosen

Physics

Book Store

Download books and chapters from book store.
Currently only available for.
CBSE Gujarat Board Haryana Board

Previous Year Papers

Download the PDF Question Papers Free for off line practice and view the Solutions online.
Currently only available for.
Class 10 Class 12

A ship A is moving Westwards with a speed of 10 kmh-1 and a ship B 100km  south of A, is moving Northwards with a speed of 10 kmh-1. The time after which the distance between them becomes shortest is

  • 0 h

  • 5 h

  • 5 square root of 2 space straight h
  • 10 square root of 2

B.

5 h

It is clear from the diagram that the shortest distance between the ship A and B  is PQ.


Here comma space sin space 45 degree space equals space PQ over OQ
rightwards double arrow space PQ space equals space 100 space straight x fraction numerator 1 over denominator square root of 2 end fraction space equals space 50 square root of 2 space straight m
Also comma space straight v subscript AB space equals space square root of straight v subscript straight A superscript 2 plus straight v subscript straight B superscript 2 end root space equals space square root of 10 squared plus 10 squared end root space equals space 10 square root of 2 space km divided by straight h
So comma space time space taken space ofr space to space reach space shortest space path space is space
straight t equals PQ over straight v subscript AB space equals space fraction numerator 50 square root of 2 over denominator 10 square root of 2 end fraction space equals space 5 straight h

It is clear from the diagram that the shortest distance between the ship A and B  is PQ.


Here comma space sin space 45 degree space equals space PQ over OQ
rightwards double arrow space PQ space equals space 100 space straight x fraction numerator 1 over denominator square root of 2 end fraction space equals space 50 square root of 2 space straight m
Also comma space straight v subscript AB space equals space square root of straight v subscript straight A superscript 2 plus straight v subscript straight B superscript 2 end root space equals space square root of 10 squared plus 10 squared end root space equals space 10 square root of 2 space km divided by straight h
So comma space time space taken space ofr space to space reach space shortest space path space is space
straight t equals PQ over straight v subscript AB space equals space fraction numerator 50 square root of 2 over denominator 10 square root of 2 end fraction space equals space 5 straight h

4490 Views

Can a body be always at rest in some frame?

Yes, a body is always at rest in a frame which is fixed with the body itself. 
746 Views

What is the most essential thing to study the motion of a body?

The most essential thing to study the motion is reference frame. Rest and motion are relative terms. It means that an object in one situation can be in rest but in another situation, the same object will be in motion. 
650 Views

What is rest?

When an object does not change its position with time, with respect to it's surroundings. In such a case the object is said to be at rest. 
1215 Views

What is motion?

When an object changes it's position with time, with respect to it's surroundings, the object is said to be in motion. 
657 Views

Is absolute rest or absolute motion possible?

Absolute rest and absolute motion is not possible because there is no point in the universe which is at rest and can be taken as point of reference. The planet Earth is in continuous motion. 
1986 Views