## How to calculate how much energy in joules?

I had a lab experiment where you had to burn the food items and place under a boiling tube and record the change of temperature. How do I work out how much energy the food provides or gave off in joules ?

Is it true that if i use 10 g of water I have to multiply it by 4.2 and then by the temperature change?

## How to flow positive charge current to the earth?

As I know if negative line fails current can be flowed by connecting to earthing wire.But when I connected the positive current direct to the surface current didn't flow. Why?

## How to solve for ΔH given change in internal energy and expansion work?

For a certain reaction at constant pressure, ΔU = -73 kJ, and 43 kJ of expansion work is done by the system. What is ΔH for this process?

Thanks for your help!! :)

## How to determine an expression for the speed of a block on an inclined plane?

A block of mass M slides from rest down a uniform plane, inclined at an angle theta to the horizontal. The coefficient of kinetic friction between the block and the slope is u. Determinean expression for the speed of the block after it has slid a distance d using:

i) Newton's second law

ii) Work-KE theorem (total work done=change in kinetic energy)

Thanks!

## How to know whether a pinned support reaction has two reactions?

I'm looking at a simple truss. Say it's been pinned in both positions, one position has a rope attached to it the other is slightly inclined (30 degrees). I know its difficult to imagine, but when should or how do I know whether or not there are less than 2 forces (Fx and Fy) acting on a simple pinned reaction?

Thank you very much

## How to find total energy of a falling ball when given kinetic and potential energy?

I don't think it's just adding the kinetic and the potential energy together, but I am not sure.

## How to build the quantum model of an atom?

For chemistry class, I need to build a quantum model of the Neon atom. I already have the configuration : 1s2 2s2 3p6, but I need to know the materials I need to buy and how I should build it. I appreciate the help :) This atom is pretty easy but a list of materials would be good.

## How to find force of friction and the friction coefficient using a graph?

If you're given a graph with applied force on then x axis and acceleration on the x axis, how do you work out the force of friction and the friction coefficient?

## How to prevent an egg from breaking in crash?

For a science project we have to fill up a 2 liter bottle with "something" and then put an egg in it. Nothing can be attached to the egg, it can only surround it. Then the bottle will be attached to a cart which will be driven into a wall. What "something" should I put in the 2 liter bottle to keep the egg from breaking?

## How to find angular acceleration of the wheel?

You are holding the axle of a bicycle wheel with radius 23 cm and mass 1.01 kg. You get the wheel spinning at a rate of 57 rpm and then stop it by pressing the tire against the pavement. You notice that it takes 1.91 s for the wheel to come to a complete stop. What is the angular acceleration of the wheel?

Please show step by step so that I can understand the thought process behind this problem.