a running man has half the kinetic energy that a boy of half his mass has.the man speed up by 1m/s and then has the same kinetic energy as the body. what were the original speeds of man and boy?

## Dual nature of light and related questions

How light has a **dual nature**?

A photon has zero rest mass. Explain how ?

(These questions were posted by Shubham SInha and Ritika Chatak)

Answer:

The dual nature of light has been established through

## Motion of connected system – A Numerical problem

A mass 5kg descending vertically,draws up a mass of3kg by means of a light string passing over a pulley.At the end of 4 seconds,the string breaks.How much higher 3 kg mass would go?

Post your solutions

## Horizontal projectile and freely falling body

A rifle at a height H aimed horizontally fires a bullet to the ground. At the same time , a bullet with the same mass in dropped from the same height. Neglecting air resistance, which one hits the ground first?Explain. ED posted Answer: Both will hit t...

## Matter, Antimatter and Einstein’s equation

It is my understanding that when antimatter comes in contact with matter that there is nothing left but pure energy. And since energy and matter are interchangeable (E=Mc2) doesn’t that mean you are actually left with all matter and no antimatter...

## How can we define one Newton ?

How can we define one Newton? (Asked Pawas Rituja) One newton is defined as that force which when acts on a body of mass 1 kg produces an acceleration of 1 m/s^2 in it Incoming search terms:if you set up your pendulum atop mount everest would the period be less than the same as or greater thanit would [...]

## A simple numerical on momentum

Car mass is 1200 kg moving velocity is 108 km/hr. On applying brakes velocity reduced to 36 km/hr. Find change in momentum? (posted by Aditi) Answer: m=1200 kg u=108 x 5/18=30m/s v=36×5/18=10m/s Change in momentum = m(v-u) = 1200 x (30-10)=1200 ...