# Search results

1. ### Job Skills Technical Interview Question Practice on QuantRiddle.com

QuantRiddle.com is a very good site to practice common technical and mathematical interview questions. It's useful and entertaining at the same time with many math and physics related information which you can see if you sign up.
2. ### Newton's Laws - Pushing on a heavy object

I'm trying to understand if a really heavy object on earth, say a mountain, would move if I push it with my bare hands. This sounds absurd but according to Newton's Laws, if I push against the mountain it will exert an equal and opposite force. I understand there are other forces like gravity...
3. ### Normal distribution

A normal distribution can be completely defined by two parameters - the mean and the standard deviation. Given a normal distribution however, say X, how can I use just the mean and the standard deviation to give me conditional expected values for X<=0 and for X>0? Im guessing the distribution...
4. ### Photoelectric Effect and metals

Can any1 explain this process and why it supposedly only works on metals.
5. ### Travelling at the speed of light?

If I was travelling at half the speed of light from A to B and another person travelling at half the speed of light from B to A (not directly towards each other, side-by-side), would i be travelling at the speed of light relative to the other person. If so, what would i see when i look at this...
6. ### After the Big Bang

Hydrogen and Helium were the main constituents formed soon (thousands of years?) after the big bang. Why did they not burn (as they are flammable), Im sure the universe was hot enough then to ignite it?
7. ### Mathematica Greatest Mathematical Puzzle of the modern age?

What is the greatest Mathematical puzzle that is unsolved? and why?
8. ### Simple vector problem

"simple" vector problem I need help on the second part of this question: The points A and B have position vectors (4i -11j +4k) and (7i +j +7k) respectively. a) Find vector equation of the line passing through the two points in terms of a parameter t. My answer: r = 4i -11j +4k + t(3i...
9. ### Integration by substitution question

How do you do this question, Ive spent hours figuring it out: Use the substitution x = 3sint to show that 3 [inte]x^2[squ](9-x^2) dx = (81/16)pi 0