Got a Lot of Potential
K + P = M
K to the E
Rollercoaster
Concepts
100
Which has the highest PE?
A 1.1 kg squirrel in a tree 10.0 m from the ground
A 0.22 kg bird in a tree 20.0 m from the ground
A 2.0 kg chipmunk in a tree 5.0 m from the ground
Mr. G (65 kg) who is levitating at 15 cm from the ground
The squirrel
100
How much mechanical energy in Joules does an object have if it has 0.50 kJ potential and 10 J kinetic energy?
510 J
100
Mr. G drops a 1.0 kg ball from 1.0 m high, what is its max KE during the fall?
9.8 J
100
Solve for original ME at station 1 (3SF)
1,960 J (or 1.96 KJ)
100
Consider a roller-coaster as we do, neglecting air resistance, rolling friction, weight shifting... Then describe what happens to ME after the coaster has began its trip downwards, after reaching the apex
ME remains constant for a system without forces to oppose / change its motion
200
SI base units for PE (the answer is not Joules)
kg*m2/s2
200
A 750 g object is pushed off a 175 m cliff. When it is 75 m from the bottom, how much ME does the object have?
1,300 J (or 1.3 kJ)
200
Mr. G drops a 1.0 kg ball from 1.0 m high, what is its max velocity during the fall?
4.4 m/s
200
Calculate the velocity at station 3 (3SF)
8.85 m/s
200
What happens when Mr. G falls out of a tree & is halfway down (regarding ME, KE & PE)?
ME is constant
PE = KE (both are 1/2 the value of ME)
300
PE of a 10 kg object that is on a ledge 10 m from the ground
980 J
300
How much mechanical energy does an object have if it is 10.0 kg, 10.0 m above the ground and is freefalling at a velocity of 10.0 m/s?
1,480 J
300
A 55 kg cliff diver is halfway to the ocean surface. If her ME = 23,716 J, Calculate her KE at this point
11,858 J
300
Calculate the KE at station 4
900 J
300
Consider a roller-coaster in a real world situation, facing air resistance, rolling friction, weight shifting & describe what happens to ME as it continues through its course after it has already plunged down the initial drop from its apex
ME decreases, until it becomes 0, so it can go again with the assistance of a chain / pulley to take it back up to the apex (sometimes assisted via braking systems)
400
An object is hanging from a hook 15 m above the ground. If it has a PE of 970 J, what is its mass?
6.6 kg
400
A 55 kg cliff diver is halfway to the ocean surface. If her ME = 23,716 J, Calculate her velocity at this point
20.8 m/s
400
A 5.0 kg projectile has 36 J of KE & a ME of 73 J, calculate the velocity
3.8 m/s
400
Calculate the velocity at station 2 (3SF)
4.43 m/s
400
Mr. G is climbing a tree at a relatively constant velocity.
At the top, he stops and the branch breaks & he falls out
Eventually he lands on the ground knocked unconscious
Explain ME during the 4 situations (climbing, just before the branch breaks, falling, & on the ground 💀)
While climbing ME increases (PE increasing, KE unchanging)
At the top, just before the branch breaks, ME = maximum, KE = 0
Falling: Increasing KE, Decreasing PE
On the ground, ME & KE = 0
500
An empty 3,300 kg elevator is 24 m above the ground level when its cables snap. What will be its maximum velocity as it falls down?
22 m/s
500
A 55 kg cliff diver is halfway to the ocean surface. If her ME = 23,716 J, Calculate her hang time up to this point
2.12 s
500
A 750 g object is pushed off a 175 m cliff. When it is 75 m from the bottom, what is the velocity of the object?
44 m/s
500
Calculate the height at station 4 (3 SF)
What is 2.16 m
500
Show (by manipulating formulas) that an object's velocity falling off a cliff that is halfway down to the ground level is mass independent, but height (and gravity) dependent
ME = PE + KE
At 1/2 h, PE = KE
mgh=1/2mv^2
2gh=v^2
v = (2gh)^1/2