







The extended real number system 
20090630 

From Justin: Hi again, thanks a lot for answering my previous question! I was also just wondering again if the extended real number system has a potential or actual infinity because it includes positive infinity as a point that exists at the end of it?
All the Best,
Justin Answered by Robert Dawson. 





Potential infinity and actual infinity 
20090629 

From Justin: Hi there, I was just wondering what is the difference between the potential infinity and actual infinity in math? Thanks a lot for your help with this question!
All the Best,
Justin Answered by Robert Dawson. 





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. 





A gymnast is swinging on a high bar. 
20070214 

From William: A gymnast is swinging on a high bar. The distance between his waist (center of mass) and the bar is 1.1 m. If his speed at the top of his swing is zero and his gain in speed is due entirely to his change in gravitational potential energy, find his speed at the bottom of his swing. Answered by Stephen La Rocque. 





Static electricity on an airplane 
20001112 

From John: What discharges an airplane of static electricity in a electric storm when it is flying. I assume the charge is on the out side of the plane but when does it get discharged, or does it occur at landing? Answered by Ted Mathie. 

