Cubical blocks of mass m and side l are piled up m a vertical column. The total

Question

Cubical blocks of mass m and side l are piled up m a vertical column. The total gravitational potential energy of a column of seven blocks is______.Assume the zero level for gravitational potential energy is at the surface on which the bottom block lays. Select the correct answer. 49/2mgl 49mgl 21mgl 39/2mgl 35mgl A champion athlete can produce one horsepower (746 W) for a short period of time. If a 75-kg athlete were to bicycle to the summit of a mountain 800-m high while expending power at this rate, she would reach the summit in_______seconds. (g = 9.8m/s^2) 1 60000 800 768 1900 .

Explanation / Answer

Question 1)Mass of system is 7m , the height of centre of gravity is 7/2 L

Potential energy is m*g*h

So PE = 7m* 7/2l*g

Option a)49/2gl

Question 2)

Power = mgh /time

So time = 75*800*9.81/746

Option d) 788

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