Answer:
Problem 8
a) Potential energy
b) Kinetic energy
c) PE initial + KE initial = PE final + KE final
d) speed = 12.52 m/s
Problem 9
The KE part should be completed with:
0 J
3750 J
7500 J
11250 J
15000 J
as shown below
Explanation:
Problem 8:
a) When the chunk of ice is at the top of the roof, it is NOT moving, and therefore its kinetic energy is ZERO, and all energy it has is potential energy (PE)
b) When it is at a fraction of an inch from the ground, The energy it has is basically Kinetic Energy (KE) due to its motion, and the potential energy is nearly zero because it distance from the ground is almost zero.
c) The conservation of energy formula stated that the total mechanical energy (given by the addition of potential energy (PE) plus the Kinetic Energy (KE) must be constant at any position of the falling chunk of ice cube in its movement downwards.
PE initial + KE initial = PE final + KE final
d) Using the equation above and the information given to us, we can estimate the speed of the ice chunk as it hits the ground:
PE initial + KE initial = PE final + KE final
(15 * g * 8) + 0 = 0 + 1/2 15 v^2
where v is the magnitude of the velocity of the chunk of ice as it hits the ground.
Solving for v:
v^2 = 2 * g * 8 = 156.8 m^2/s^2
v = 12.52 m/s
Problem 9:
We used the conservation of Total mechanical energy given above:
PE initial + KE initial = PE final + KE final to obtain:
PE KE
15000 J 0 J
11250 J 3750 J
7500 J 7500 J
3750 J 11250 J
0 J 15000 J
