Answer:
D. Friction
Explanation:
Friction is a force that opposes motion. So a perpetual motion machine can never be built because it is impossible to eliminate frictional force. It can only be reduced
Answer:
Let R1= resistance of 4ohms
R2= resistance of 8ohms
Equivalent resistance R will be
R=R1 + R2
=> 4+8=12ohms
The current through the two resistors will be the same since they are connected in series. Notwithstanding, the voltage will drop to appreciate the change.
Explanation:
Answer:
a) The electric field at that point is 
newtons per coulomb.
b) The electric force is 
newtons.
Explanation:
a) Let suppose that electric field is uniform, then the following electric field can be applied:
(1)
Where:
- Electric field, measured in newtons per coulomb.
- Electric force, measured in newtons.
- Electric charge, measured in coulombs.
If we know that 
and 
, then the electric field at that point is:
The electric field at that point is newtons per coulomb.
b) If we know that and 
, then the electric force is:
The electric force is newtons.
Answer:
his speed is 5cm a second
Answer:
F = - k (x-xo) a graph of the weight or applied force against the elongation obtaining a line already proves Hooke's law.
Explanation:
The student wants to prove hooke's law which has the form
F = - k (x-xo)
To do this we hang the spring in a vertical position and mark the equilibrium position on a tape measure, to simplify the calculations we can make this point zero by placing our reference system in this position.
Now for a series of known masses let's get them one by one and measure the spring elongation, building a table of weight vs elongation,
we must be careful when hanging the weights so as not to create oscillations in the spring
we look for the mass of each weight
W = mg
m = W / g
and we write them in a new column, we make a graph of the weight or applied force against the elongation and it should give a straight line; the slope of this line is sought, which is the spring constant.
The fact of obtaining a line already proves Hooke's law.
