This question is written wrong, I think u meant 20 kg?
Answer:
7560 Joules
Explanation:
= Mass of first car = 
= Mass of second car = 
= Initial Velocity of first car = 0.3 m/s
= Initial Velocity of second car = -0.12 m/s
v = Velocity of combined mass
As linear momentum of the system is conserved

Energy lost is

The Energy lost in the collision is 7560 Joules
Answer:
7.2 V
Explanation:
The three batteries are connected in series to the terminals of the phone: it means that they are connected along the same branch, so the current flowing through them is the same.
This also means that the potential difference across the phone will be equal to the sum of the voltages provided by each battery.
Here, the voltage provided by each battery is
V = 2.4 V
So, the overall voltage will be
V = 2.4 V + 2.4 V + 2.4 V = 7.2 V
Explanation:
electrical potential = (6.6-3.4)/0.20
= 16 uc/m