Circuits
If a circuit has elements only in series, how should the arrow heads with tails and starbursts look?
They should all be the exact same
Is work positive or negative for the following:
1) An object is risen from 5 m to 10 m.
2) A car slams into a tree and the tree stops its movement.
3) A crane tries to lift a box, but is unable to because the box is too heavy.
1) Positive
2) Negative
3) Zero
If a positive object goes near a neutral object, why are the objects attracted to each other?
The neutral object's electrons move towards the positive object. So, it becomes polarized and will then attract to the positive object.
Rank the following circuits from highest to lowest flow:
A) A circuit with two parallel paths each with one resistor
B) A circuit with three resistors, all in series
D) A circuit with one series resistor
Highest
A
D
B
Lowest
A certain blue whale weighs 136,000 kg (~300,000 lbs), and is moving at a speed of 0.5 m/s. What is the kinetic energy of the blue whale?
KE = 1/2 x m x v2
KE = 17,000 J
What does it mean for two variables to be directly proportional?
What does it mean for them to be indirectly proportional?
Give an example of each.
Directly proportional - Increasing one increases the other. Caffeine and energy. Increase caffeine, energy increases.
Inversely proportional - Increasing one decreases the other. Sadness and energy. Increase amount of sadness will decrease energy.
Two resistors are in parallel. One resistor has 5 Ω and the other has 15 Ω.
1) How does the current through them compare?
2) How does their voltages compare?
1) Current is higher through the 5 Ω resistor
2) Voltage is equal since they are in parallel
A 2.5 kg ball slams into a wall. If the ball was traveling at 11 m/s, what is the work done by the wall to stop the ball?
KE = W
W = - 151.25 J
If the distance between the charge doubles the force will be
The force also doubles
There are two resistors in a circuit. One has 12 Ω of resistance and the other has 8 Ω of resistance.
1) What is their resistance if they are in parallel?
2) What is their resistance if they are in series?
1) Parallel: 4.8 Ω
2) Series: 20 Ω
An 0.5 kg feather moves from 5 m to 0 m. If their final velocity is 5 m/s
1) What is the work done by air resistance?
2) Calculate the force of friction.
W = 18.25 J
F = 3.65 N
A piece of fur gets a charge of +0.3 C after rubbing against a plastic rod.
1) How many electrons were transferred?
2) What is the charge of the plastic rod?
1) 1.58*1018 electrons
2) -0.3 C
Two bulbs are in series. One has 10 Ω and the other has 2 Ω.
1) Which will be brighter?
2) How does the amount of current through them compare? (AKA the arrowhead with tails)
1) The 10 Ω will be brighter?
2) Current is the same! But the one with more resistance will be thinner, so there will be more electrons inside at a given time.
A 110 kg skateboarder travels from 10 m to an unknown height. If the velocity at the unknown height is 8 m/s, what is this height? (Assume that there is no work done by friction)
Total Starting Energy = 10780 J
Total Final Energy = 10780 J
Final KE = 1/2 mv^2
Final KE = 3520 J
Final PE = 10780 - 3520 = 7260 J
Final PE = mgh
7260 = (110)(9.8)h
h = 6.7 m
If the force between two charges is 10N, what would the force be if each charge was doubled and the distance was halved
80N