Wednesday, September 14, 2011

CoE questions

PFY p.121
Image001

a) Weight = mg
= 50x10
= 500 N
b) GPE = mgh
= 500x4
= 2,000 J
c) Total energy at start = Total energy at end
= 2,000 J 

Collins, p.91
Image002
a) GPE = mgh
= 35x10x30
= 10,500 J
b) Energy at start = Energy at end
KE = (1/2)mv^2
10500 = (1/2)x35xv^2
600 = v^2
v = 10√6 = 24.5 m/s
c) Because the friction force causes the sledge to slow down, therefore the velocity is lesser than what we calculated, as well as the air resistance. 


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