An object of mass 0.25kg moves at a height h above the ground with a speed of 4ms-1, if its mechanical energy at this height is 12 J, determine the value of h. [g = 10ms-1]
A
0.8m
B
4.0m
C
4.8m
D
5.6m
Verified Correct Answer: B.
Physical Principles & Numerical Solution
The total mechanical energy E at height h is given by: E = PE + KE
E = mgh + \(\frac{1}{2}\)mv\(^2\)
12 = (0.25 x 10 x h) + (0.5 x 0.25 x 4 x 4)
12 = 2.5h + 2
2.5h = 12 - 2 = 10
h = \(\frac{10}{2.5}\) = 4m.
Source: Myschool Past Questions Archive (Record #35031)