an artificial satellite of mass 900 kg is lunched at a speed of 11,000m/s from its launching station. how much is the kinetic en
1 answer:
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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
Answer:
Approximately (assuming that the car was on level ground.)
Explanation:
When an object of mass is moving at a speed of
, the kinetic energy of that object would be
.
Initial kinetic energy of the car:
.
After the car comes to a stop, the kinetic energy of this car would be because the car would not be moving.
Change to the kinetic energy of the car: .
If the car is traveling on level ground, friction would be the only force that contributed to this energy change. Hence:
.
The value of the work that friction did is negative. The reason is that at any instant before the car comes to a stop, friction would be exactly opposite to the direction of the movement of the car.
The work of a force on an object is the dot product of that force and the displacement of that object. The dot product of two vectors of opposite directions is negative. Hence, in this question, the work that friction did on the car would be negative because the friction vector would be opposite to the movement of the car.