The ball can't reach the speed of 20 m/s in two seconds, unless you THROW it down from the window with a little bit of initial speed. If you just drop it, then the highest speed it can have after two seconds is 19.6 m/s .
If an object starts from rest and its speed after 2 seconds is 20 m/s, then its acceleration is 20/2 = 10 m/s^2 .
(Gravity on Earth is only 9.8 m/s^2.)
Answer:
Energy density will be 14.73 
Explanation:
We have given capacitance 
Potential difference between the plates = 365 V
Plate separation d = 0.200 mm 
We know that there is relation between electric field and potential
, here E is electric field, V is potential and d is separation between the plates
So 
Energy density is given by
Answer:
5 ohms
Explanation:
Given:
EMF of the ideal battery (E) = 60 V
Voltage across the terminals of the battery (V) = 40 V
Current across the terminals (I) = 4 A
Let the internal resistance be 'r'.
Now, we know that, the voltage drop in the battery is given as:
Therefore, the voltage across the terminals of the battery is given as:

Now, rewriting in terms of 'r', we get:

Plug in the given values and solve for 'r'. This gives,

Therefore, the internal resistance of the battery is 5 ohms.
Aperture is measured in F-stops, in which the f-stops is the amount of light allowed to pass through the aperture, which simply put means that the smaller the aperture, the higher the f-stops. What it does is reduce the amount of light that reaches the film, so the higher the f-stops, the less light reaches the film.