Answer:
71195 seconds or 19.8 hours
Explanation:
Because the steel will be melted, beginning from room temperature, energy is needed to heat it from room temperature to 1600°C and another to melt it at 1600°C.
We take room temperature to be 27°C, the specific heat capacity of steel to be 420 J/kg/K and the specific latent heat of fusion of steel to be 440 J/kg.
The heat required to heat the steel from room temperature to 1600°C is given by

is the mass,
is the specific heat capacity and
is the change in temperature.

The heat required to melt it at 1600°C is

is the mass and
is the specific latent heat of fusion of steel.

Adding both, the heat required is 
Because the oven is 65% efficient, its output power = 
Now, energy = power * time
Time = Energy/power

Optical Telescopes....................................
Answer:
a).
b).
c).
Explanation:
a).
The acceleration for definition is the derive of the velocity so:





Replacing

b).
If the pulsar will continue to decelerate at this rate, it will stop rotating at time:




c).
582 years ago to 2019
1437

(C) have the same heat capacity