Answer : The correct option is, (d) 
Explanation :
In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.


where,
= specific heat of copper = 
= specific heat of water = 
= mass of copper = 120 g
= mass of water = 300 g
= final temperature of mixture = 
= initial temperature of copper = ?
= initial temperature of water =
Now put all the given values in the above formula, we get:


Therefore, the temperature of the kiln was, 
Answer:
Yes, the capacitor's Q load varies inversely proportional to the distance between plates.
Explanation:
In the attached files you see the inverse relationship between capacity and distance between plates "d".
In the following formula we see its relationship with the "Q" load
The ball has an initial speed of 10m/s. This is because it is moving with the balloon. Now the balloonist throws the ball 4m/s with respect to himself, so it means that he gives the ball a extra push of 4m/s, so the total speed is 14m/s. Since it takes 30 seconds to reach the ground, the distance travelled is 14*30=420m.
Answer:(a)891.64 N
(b)0.7
Explanation:
Mass of crate 
Crate slows down in 
initial speed 
inclination 
From Work-Energy Principle
Work done by all the Forces is equal to change in Kinetic Energy




change in kinetic energy

(b)Coefficient of sliding friction



and 

