IIT JEE , AIEEE Forum - Physics , Mechanics - Simple assertion-reason....

Ronaldooo

1)A box is falling freely.Inside the box,a particle is projected with some velocity v w.r.t box at an angle theta.
Assertion-The path of the particle w.r.t an observer sitting in the box will be a straight line.
Reason-The acceleration of the particle w.r.t box is 0.

2)Assertion-Water kept in 2 vessels A and B at 4⁰C.Vessel A is heated while vessel B is cooled.Volume of water in A will increase while volume of water in B will decrease.
Reason-On heating,volume of water increases.

Plzz reply asap.

karthik2007

1) Assertion and Reason should be true.

junglejalebi

for second one
volume of water is minimum at 4celcius
both are correct and reason is correct expalanation

Ronaldooo

How come assertion is true.The path should be parabolic right??Because,both the observer and the particle are in the same frame.

karthik2007

Note that it falls freely, hence force of gravity is negated in the box

karthik2007

Mathematically:
forces acting on the stone are:

mg downwards
Pseudo force mg upwards.

hence net force is zero

computer001

no the acc wrt them is 0..
a similar q is here..chk out my proof
http://www.goiit.com/posts/list/mechanics-check-your-concept-49836.htm#250676

junglejalebi

first one assertion and reason are both true
admit the answer of mr karthick

karthik2007

Computer, the two questions are not related to each other. In fact, myself and feynmann solved the same question a few months ago on the same forum.

Ronaldooo

Ok...thanx karthik...
@jungle jalebi
But reason does not explain the assertion fully as when water is cooled at 4⁰C,its volume decreases due to anomalous behavior of water.

computer001

the 2 are related:
wrt th fact tht durin motion of same acc the rel motion is a st line...
its slighta different but it amts to the same thing u no..

karthik2007

The exact motion of the ball will be:

It will travel on the line making an angle @ with the box's surface (floor), till it whacks the top, then will rebound back, whack the bottom, and then again go to the top.... this goes on.

computer001

er...isnt tht obvious...
consider wrt to lift...acc of ball is 0...
so obviously it will be movin wid const vel...so assuming it is elastic collision obviously it will htit top ,then bottom n so on!

Ronaldooo

What abt the 2nd one??

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