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Motion in Straight Line

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Physics Part I

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Physics

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
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 ?

Velocity space of space car space straight A comma space straight v subscript straight A space end subscript equals space 36 space km divided by straight h space equals space 10 space straight m divided by straight s space

Velocity space of space car space straight B comma space straight v subscript straight B space equals space 54 space km divided by straight h space equals space 15 space straight m divided by straight s space

Velocity space of space car space straight C comma space straight v subscript straight C space equals space 54 space km divided by straight h space equals space 15 space straight m divided by straight s

Relative space velocity space of space car space straight B space with space respect space to space car space straight A comma space space

straight v subscript BA space equals space straight v subscript straight B space – space straight v subscript straight A space equals space 15 space – space 10 space equals space 5 space straight m divided by straight s space

Relative space velocity space of space car space straight C space with space respect space to space car space straight A comma space space

straight v subscript CA space end subscript equals space straight v subscript straight C space – space left parenthesis – space straight v subscript straight A right parenthesis space equals space 15 space plus space 10 space equals space 25 space straight m divided by straight s space

At space straight a space certain space instance comma space both space cars space straight B space and space straight C space are space at
space the space same space distance space from space car space straight A space straight i. straight e. comma space space straight s space equals space 1 space km space equals space 1000 space straight m space

space Time space taken space left parenthesis straight t right parenthesis space by space car space straight C space to space cover space 1000 space straight m space equals space 1000 space divided by space 25 space equals space 40 space straight s space

Hence comma space to space avoid space an space accident comma space car space straight B space must space cover
space the space same space distance space in space straight a space maximum space of space 40 space straight s.

space From space second space equation space of space motion comma

minimum space acceleration space left parenthesis straight a right parenthesis space produced space by space car space straight B space can
space be space obtained space as colon

space straight s space equals space ut space plus space left parenthesis 1 divided by 2 right parenthesis at squared space 1000 space

space space space equals space 5 space cross times space 40 space plus space left parenthesis 1 divided by 2 right parenthesis space cross times space straight a space cross times space left parenthesis 40 right parenthesis squared space straight a

space space space equals space 1600 space divided by space 1600 space equals space 1 space ms to the power of negative 2 end exponent
228 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

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

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