1) Potential energy before the fall: 98 J
The gravitational potential energy of an object is given by:
[tex]U=mgh[/tex]
where m is the mass of the object, g is the gravitational acceleration and h the heigth of the object above the ground.
In this problem, m = 2 kg, g = 9.8 m/s^2 and h = 5 m: substituting into the equation, we find
[tex]U=(2 kg)(9.8 m/s^2)(5 m)=98 J[/tex]
2) Work done by gravity: 98 J
The work done by a force is given by:
[tex]W=Fd cos \theta[/tex]
where
F is the magnitude of the force
d is the displacement of the object
[tex]\theta[/tex] is the angle between the direction of the force and the displacement
In this problem:
[tex]F=mg=(2 kg)(9.8 m/s^2)=19.6 N[/tex]
d = 5 m
[tex]\theta=0^{\circ}[/tex]
Therefore,
[tex]W=(19.6 N)(5 m)(cos 0^{\circ})=98 J[/tex]
