Let F1=Force exerted by the brother (+F1)
F1= Force exerted by the sister (-F2)
Fnet=(+F1) + (-F2)
Fnet= (+F1) + (-F2)
Fnet=F1 - F2
Fnet= (+3N)+(-5N)
Fnet= -2N
-F
towards the sister (-F) (greater force applied)
Answer:
The energy is 
(a) is correct option
Explanation:
Given that,
Energy = 4480 j
Weight of nitrogen = 20 g
Boil temperature = 77 K
Pressure = 1 atm
We need to calculate the internal energy
Using first law of thermodynamics


Put the value into the formula



We need to calculate the number of molecules in 20 g N₂
Using formula of number of molecules

Put the value into the formula


We need to calculate the energy
Using formula of energy

Put the value into the formula


Hence, The energy is 
Freezing (liquid to solid)
Deposition (gas to solid)
Condensation (gas to liquid)
All three of these state changes are a result of a energy loss. When considering energy loss it is best to think of situations where temperature has dropped. Less energy in the system results in less energy the substance is exposed to or has available.
By compressing the spring a distance <em>x</em> (in m), you are storing 1/2 <em>k</em> <em>x</em> ² (in J) of potential energy, which is converted completely into kinetic energy 1/2 <em>m v</em> ², where
• <em>k</em> = 40 N/m = spring constant
• <em>m</em> = 10 kg = mass of the ball
• <em>v</em> = 2 m/s = ball's speed (at the moment the spring returns to its equilibrium point)
So we have
1/2 <em>k</em> <em>x</em> ² = 1/2 <em>m</em> <em>v</em> ²
<em>x</em> = √(<em>m</em>/<em>k</em> <em>v</em> ²) = √((10 kg) / (40 N/m) (2 m/s)²) = 1 m