12 V is the f.e.m.
of the battery. The potential difference that is applied to the motor is actually the fem minus the voltage drop on the internal resistance r:
this is equal to the voltage drop on the resistance of the motor R:
so we can write:
and using
and
we can find the current I:
One of the concepts to be used to solve this problem is that of thermal efficiency, that is, that coefficient or dimensionless ratio calculated as the ratio of the energy produced and the energy supplied to the machine.
From the temperature the value is given as
Where,
T_L = Cold focus temperature
T_H = Hot spot temperature
Our values are given as,
T_L = 20\° C = (20+273) K = 293 K
T_H = 440\° C = (440+273) K = 713 K
Replacing we have,
Therefore the maximum possible efficiency the car can have is 58.9%
There are some missing data in the text of the problem. I've found them online:
a) coefficient of friction dry steel piston - steel cilinder: 0.3
b) coefficient of friction with oil in between the surfaces: 0.03
Solution:
a) The force F applied by the person (300 N) must be at least equal to the frictional force, given by:
where
is the coefficient of friction, while N is the normal force. So we have:
since we know that F=300 N and
, we can find N, the magnitude of the normal force:
b) The problem is identical to that of the first part; however, this time the coefficienct of friction is
due to the presence of the oil. Therefore, we have:
repeated mesurement can reduce the error
it is true
if you take any mesurement repeatedly and the average is taken, the error will be less
Answer:
Given,
mass of man = 100 N = 10 kg
height = h = 25m
since the man does not move anything with his force, work done by him is zero
work done on the man = gain in potential energy
P.E=mgh
P.E=10×9.8×25
P.E=2.45KJ
Explanation:
so, potential energy gained by man is 2.45 KJ
