2. Recall the equation for an object's gravitational potential energy (assuming relative to the surface of the earth):
PE = mgh
PE is the potential energy.
m is the object's mass.
g is the acceleration due to earth's gravity.
h is the object's height from the earth's surface.
Given values:
PE = 19600 J
m = 100 kg
g = 9.81 m/s²
Substitute the terms in the equation with the given values and solve for h:
19600 = 100×9.81×h
h = 19.98 m
3. Recall the equation for an object's kinetic energy:
KE = 0.5mv²
KE is the kinetic energy.
m is the object's mass.
v is its velocity.
Given values:
KE = 25 J
m = 2 kg
Substitute the terms in the equation with the given values and solve for v:
25 = 0.5×2v²
v = 5 m/s
Use the equation for an object's potential energy again:
PE = mgh
Given values:
PE = 98 J
m = 2 kg
g = 9.81m/s²
Substitute and solve for h:
98 = 2×9.81×h
h = 4.99 m
