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# Tag Archives: doubt

## Optics

Rajat asked:

“when we exchange the lenses of compound microscope, then why it does not act as a telescope?”

## EXCEEDING COSMIC LIMIT

ADITYA KIRAN asks:

“i’ve a beautiful doubt…normally we believe that nothing in dis world can cross cosmic limit…now suppose if 2 light particles(velocity=c) collide at right angles,,then their resultant will be [c*root2]…but that is greater than cosmic limit,right?????”

LET THE VISITORS RESPOND

## Sequence of Learning Physics

In what sequence should these chapters be prepared for my exams:-

units and dimensions,kinematics,laws of motion,work power and energy,motion of system of particles and rigid body dynamics,gravitation.

Apoorv Katoch asked

Answer:

It is better to follow the same pattern as given in NCERT text book

## Problem from Kinematics

The speed of a train changes from36km/h to 72km/h in 10sec. calculate the distance travelled during this time

**Answer**:

u=36km/h = 10 m/s

v=72 km/h=20 m/s

t=10 s

S=?

use **v = u+ at** to find a

a = 1 m/s^{2}

Use **v ^{2}-u^{2}=2aS** to find S

S = (400-100)/2 = **150 m**

## Now users at Ask Physics can add equations to their comments and questions.

Ask Physics has installed the Latex server and now users can type latex code to insert complex equations to their comments or questions.

If you are not familiar with latex code, use the following site to generate the code for the equation that you need.

http://www.codecogs.com/latex/eqneditor.php

When you visit the above site you can edit and view the result of the code generate. You have the option to copy the image of the equation or to copy the code itself (what you typed for getting the image equation; not the html code supplied) and paste the code in your comment.

Go, Try it Now!

## Find time of death of patient with differential equations

**Mr. N.P. Sahani** asked:

“The differential equation and solution for finding the time of death of a patient”

**Answer:**

See that the question is to find the time of death (Not predicting the time of death. I thought that when I read it first.)

I can give some links which will be helpful in this connection

- http://www.exploreforensics.co.uk/estimating-the-time-of-death.html
- http://en.wikipedia.org/wiki/Thermal_death_time
- http://autarkaw.wordpress.com/2008/07/21/time-of-death-a-classic-ode-problem/
- http://people.uncw.edu/lugo/mcp/DIFF_EQ/deproj/death/death.htm
- http://mathforum.org/library/drmath/view/53409.html
- http://www.scribd.com/doc/21514655/Newton-s-Law-of-Cooling-Finding-the-Time-of-Death-of-a-John-Doe