A 10 kg rock that has been dropped from a 60 meter high cliff experiences a average force of air resistance of 30 N. Calculate the KE at the bottom of the fall.
"KE is equal to the gravitational potential change minus the work against friction"
KE = PE - (height * frictional force)
KE = gravitational potential change - work against friction
KE = (m g h) - (60 m * 30 N)
mgh does not help me I don't know what it means
my book says PE gravity= mgh this is why I'm getting confused my book calls mgh PE and you say KE??
ok so KE=PE gravity
which is mgh - h x friction force
(10*9.80*60)-(60*30)
=4080 J
To calculate the kinetic energy (KE) at the bottom of the fall, we need to consider two components: the gravitational potential energy (GPE) lost during the fall and the work done against air resistance.
1. Calculate the gravitational potential energy (GPE) lost:
GPE = m * g * h
Given:
Mass (m) = 10 kg
Acceleration due to gravity (g) = 9.8 m/s^2
Height (h) = 60 m
GPE = 10 kg * 9.8 m/s^2 * 60 m
GPE = 5880 J
2. Calculate the work done against air resistance:
Work = Force * distance
Given:
Force (F) = 30 N
Distance (d) = 60 m
Work = 30 N * 60 m
Work = 1800 J
3. Calculate the kinetic energy (KE) at the bottom of the fall:
KE = GPE - Work
KE = 5880 J - 1800 J
KE = 4080 J
Therefore, the kinetic energy (KE) at the bottom of the fall is 4080 J.