Cassaundra

A 0.77 kg mass, attached to the end of a 0.86 m string, is whirled around in a circular horizontal path. If the maximum tension that the string can withstand is 683 N, then what maximum speed can the mass have if the string is not to break?

Balance each of the following redox reactions and classify it as a combination, decomposition or displacement reaction. a) Mg(s)+H2O(g)->Mg(OH)2(s)+H2 b) Cr(NO3)(aq)+Al(s)->Al(NO3)(aq)+Cr(s) c) PF3(g)+F2(g)->PF5(g)

I know how to balance, I have no idea what the heck any of the classifications are