 Welcome to my physics webpage. The purpose of this is to showcase our class's physics notes of the year. Im in grade 10, and doing this project for extra marks in my class. Please take a look and if you have any questions / comments please email me here. Quick Reference: - Sig. Digs. - - Slope - - Work - - Energy - - Links - page optimized for resolutions 800 x 600 and above  Significant digits are also known as "Sig. Figs", as in significant figures. Both mean the same thing, and serve the same purpose. Some simple rules to follow: 1) Zero's that come before a number (at the start) DO NOT count. Example: 0.123 = 3 Sig. Digs. 2) Zero's however, that come following a number DO count. Example: 1.023 = 4 Sig. Digs. Adding & Subtracting Sig. Digs. When adding or subtracting, the answer will have the same number of decimal places as the 'least accurate number' (the one with the least # of decimal places) in the equation. Example: 2.0 + 2.31 = 4.31 = 4.3 Example: 100.17 - 12.2 = 87.97 = 88.0 Multiplying & Dividing Sig. Digs. When multiplying or dividing, your answer will have the same number of digits of the one in the question that has the least number of sig. figs. Example: 4.000 / 2.0 = 2.0 If your answer must have less sig. figs, use 'scientific notation'. Example: 344 x 2 = 688 = 7 x 10 2 *make sure you round first*  Velocity can be defined as a term describing an object's speed and direction of motion. A.K.A Speed. We want to calculate the slope of a distance/time graph to get the object's velocity, or speed. Thus, we use the formula:  In simpler form, Velocity or speed is equal to distance divided by time. Remember Delta means a change in something. If you are trying to find the acceleration, simply divide the velocity (metres/seconds) into time (seconds). The seconds units would cancel eachother out leaving you with just metres. Overview: Q. What does a speed of 100 km/h mean? A. This is the distance that a object can travel in one hour. Q. How are the units for speed and the units for the slope of a position-time graph related? A. They are related by speed (metres/sec.) and slope, (distance/time). Q. What does the slope of a position-time graph tell you about the motion of an object? A. The more slope will indicate that the speed is faster of the object. The slope of a distance/time graph represents velocity. The slope of a velocity/time graph represents acceleration. The area under a velocity/timegraph represents distance.   For a time of 3 seconds, the student travelled with a constant speed of 2 m/s. Then, for a time of 3 seconds, the student did not move at all. (0 m/s)  To A scientist, work measures the transfer of energy from one object to another. When work is done ON a object, it gains energy. We call this a energy transfer. Work is done on such things as: How do physicists calculate the amount of work done on a object? Formula: W = F x D Meaning of each symbol: Work = Force x Distance Units for each quantity: Work= Joules (J) Force= Newtons (N) Distance= Metres (M) A few examples: A 1 kg weight is moved 4 metres across the floor. Calculate the work done. Remember, 1 kg = 10 n W=FxD W=10n x 4m=40nm = 40j = 4 x 101 A desk is pushed against a door. The desk doesn't move. Desk=10kg. Calculate the work. W=FxD 10kg= 100n x 0m= 0j  Potential Energy- Energy possessed by an object due to it's position or condition. Kinetic Energy- Energy possessed by an object to to motion. Remember: A) In a mechanical system, (the energy of a moving object) work is associated with a change in position (potential energy) or a change in velocity (kinetic energy); that is, changes in mechanical energy. -Example- -Pushing a car out of mud- Work on done ON the system. The system's energy INCREASES, and results in a change in KINETIC energy. B) In a thermodynamic system, work is associated with a change in temperature (associated with thermal energy) or chemical composition (associated with chemical bond energy); that is changes in internal energy. -Example- -If a paperclip is bent rapidly back and forth 20 times- Work is done ON the paperclip, so the energy level must INCREASE. There is NO overall change in mechanical energy, but there IS change in internal energy. There is NO change once again in chemical combustion, and because of friction, there IS a temperature change which will rise. C) As time passes, the energy of a system may be converted from one form to another. -Example- A pendulum (a mechanical system)  Ek= Kinetic Energy Epg= Potential Gravitational Energy To do useful work, potential energy must be converted to some other form of energy. -Examples- 1) useful work performed: pile driver into ground energy conversion: potential to kinetic 2)useful work performed: muscle movement/contaction energy conversion: chemical to kinetic 3) useful work performed: lighting a room energy conversion: electrical to light/thermal Energy Conversion Calculation: A 1.75 kg electric car is run for 3 minutes from a 60 Watt energy source. Calculate the velocity of the electric car.  Power Conversion Calculation: An elevator motor develops 32 kW (1000 watts) of power while it lifts the elevator 24m at a constant speed. If the elevator mass is 2200 kg, including the passengers, how long does the motion take?  Energy Efficiency:  Remember the Output Energy is ALWAYS the smallest number. If the Input energy is 29913 J and the output energy is 13305 J then what is the efficiency? 13305 J / 29913 J x 100 = 44.478 J A man uses a 300 W tea kettle to heat 152 ml of water. He plugs the kettle in and after 2 minutes the temperature has gone from 12 C to 39 C. How efficiant is the tea kettle?  Electrical Potential Energy Ee=qV Ee= Electrical Energy (Joules) q= Energy (Coulomb) V= Voltage (Volts) How much energy is stored in a battery if the voltage is 14 volts and there are 18.9 coulombs in the battery? Ee=qV Ee= 18.9c x 14v = 264.6 J = 2.7 x 10 J2 How much charge is stored in a 14.0 volt battery that stores 176.4000 J of energy? Q= Ee / V 176.4000j / 14.0v = 12.6 c Kinetic Energy Due To Motion E= 1/2 mv 2 A bowling ball with a mass of 1.23 kg is travelling at a velocity of 4.03 m/s and smashes into a wall. How much energy does the bowling ball have when it hits the wall? E= .5 x mv2 .5 x 1230g x 4.03m/s = 2.5 x 103  Here are a few links I've found all over the internet which helped me grasp certain physics concepts. Check them out. Catholic Memorial Physics Page How Things Work From A Physics Concept A Century Of Physics Contribution By Women To Physics The Physics Of Everyday Things Physics News Physics 2000 The Physics Classroom All content (information, graphics, etc.) property of Ryan Organ, January 2000 |
