







A piecewise graph 
20140510 

From Zoe: Lightning Energy charges residential users for each unit of electrical energy bought from them each quarter, according to the scale below:
0500 units cost 17 cents per unit
5001500 units cost $85 plus 10 cents for each unit in the excess of 500
1500 or more units cost $185 plus 9 cents for each unit in excess of 1500
Sketch a graph showing the charge C as a function of U for up to 2000 electricity units Answered by Penny Nom. 





Energy in calories 
20091215 

From Josephine: A soft drink manufacturer claims that a new diet soft drink is now "low Joule". The label indicates that the available energy per serving is 6300 J. What is the equivalent of this energy in calories? (1 Calorie=1000 cal) Answered by Robert Dawson. 





e = m c^2 
20091209 

From Jim: Please explain the following formula:
E=MC2 (squared) Answered by Robert Dawson. 





Electrical energy 
20081209 

From ROHAN: A lamp consumes 1000J of electrical energy in 10s. what is its power Answered by Stephen La Rocque. 





A falling block 
20081018 

From KOBINA: A 50 kg block being held at rest 20m above the ground is released. the block falls (no friction). how fast is the block traveling (in m/sec) when it has lost 40% of its original potential energy. Answered by Stephen La Rocque. 





Braking Distance Relationship 
20080723 

From Mr.Adjetey: you are travelling at 30km/h.According to the rule of thumb,the braking distance is 9 metres when braking normally.How long is the braking distance under the same conditions when travelling at 60km/h? Answered by Janice Cotcher. 





Rotational energy needs 
20070829 

From will: how much energy in KW do i need to start and subsequently rotate a 4 ton fly wheel of 1 metre radius at 12 rpm? Answered by Stephen La Rocque. 





Physics/Temperature Change 
20070422 

From William: A 3.00 x 10^3 kg lead bullet travels at a speed of 2.40 x 10^2 m/s and hits a wooden post. If half the heat energy generated remains with the bullet, what is the increase in temperature of the embedded bullet? (specific heat of lead = 1.28 x 10^2 J/kg) Answered by Stephen La Rocque. 

