Answer:
F=ma
Explanation:
Force = mass * acceleration
The comets hit the moon's surface because there is no atmosphere on the moon to protect it. The earth has an atmosphere so it is protected.
Answer:
The efficiency is 0.33, or 33%.
Explanation:
From the thermodynamics equations, we know that the formula for the efficiency of a heat engine is:

Where η is the efficiency of the engine, Q_1 is the heat energy taken from the hot source and Q_2 is the heat energy given to the cold object. So, plugging the given values in the formula, we obtain:

This means that the efficiency of the heat engine is 0.33, or 33% (The efficiency of an engine is dimensionless).
Answer:
226.2 m/sec
Explanation:
We have given 
The plank's constant 
Mass of electron 
Now according to Heisenberg uncertainty principle 
So