Answer:
(a) 0 kJ
(b) 9.81 kJ
(c) 31.32 m/s
Explanation:
(a)
From the law of conservation of energy, energy can only be transformed from one state to another. At a height of 50 m, all the kinetic energy is converted to potential energy hence KE=0
(b)
Potential energy, PE=mgh where m is the mass, g is acceleration due to gravity and h is the height
Substituting 50 m for h and 20 Kg for m, taking g as 9.81 then
PE=20*9.81*50=9810 J=9.81 kJ
(c)
Relating the equation of potential energy to the equation of kinetic energy, which is [tex]0.5mv^{2}[/tex]
[tex]mgh=0.5mv^{2}[/tex] where v is the velocity of the mass
[tex]v=\sqrt {2gh}[/tex]
Substituting 50 m for h and taking g as 9.81 then
[tex]v=\sqrt {2*9.81*50}=31.32091953\approx 31.32 m/s[/tex]
