Of the materials listed wood is the best insulator. It would be the least hot if exposed to similar temperatures.
It’s solved by using a pretty standard formula for efficiency.
Explanation:
Given that,
Linear speed of both disks is 5 m/s
Mass of disk 1 is 10 kg
Radius of disk 1 is 35 cm or 0.35 m
Mass of disk 2 is 3 kg
Radius of disk 2 is 7 cm or 0.07 m
(a) The angular velocity of disk 1 is :

(b) The angular velocity of disk 2 is :

(c) The moment of inertia for the two disk system is given by :

Hence, this is the required solution.
Answer:
The tension in the string is 16.24 N
Explanation:
Given;
mass of the sphere, m = 1.55 kg
initial velocity of the sphere, u = 2.81 m/s
final velocity of the sphere, v = 4.60 m/s
duration of change in the velocity, Δt = 2.64 s
The tension of the string is calculated as follows;

T = 1.55(0.678 + 9.8)
T = 1.55(10.478)
T = 16.24 N
Therefore, the tension in the string is 16.24 N
Answer:
It's impossible for an ideal heat engine to have non-zero power.
Explanation:
Option A is incomplete and so it's possible.
Option B is possible
Option D is related to the first lae and has nothing to do with the second law.
Hence, the correct option is C.
The ideal engine follows a reversible cycle albeit an infinitely slow one. If the work is being done at this infinitely slow rate, the power of such an engine is zero.
We can also stat the second law of thermodynamics in this manner;
It is impossible to construct a cyclical heat engine whose sole effect is the continuous transfer of heat energy from a colder object to a hotter one.
This statement is known as second form or Clausius statement of the second law.
Thus, it is possible to construct a machine in which a heat flow from a colder to a hotter object is accompanied by another process, such as work input.