When a storm is formed, the storm clouds contain negative charges and the ground is filled with positive charges. Similar to the way magnets work the two are attracted. The the collision of the two charges produce an electrical discharge.
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When you are talking about the Principle of mechanical Energy Conservation, it is really only including the kinetic and potential energy in a total system. When frictional forces are present, although the conservation of energy law is still present, it does not work when it comes to the conservation of mechanical energy as there is another type of energy that is factored in. As friction acts on the object, that transition from potential to kinetic as it slide/falls will be completely different as some of that energy is being transformed into thermal energy. Which breaks the conservation of mechanical energy.
final velocity = 0
acceleration = - 10 m/ s 2
distance. = 20 m
u = ?
v^2 - u ^2 = 2 a s
0^2 - u^ 2 = 2 * -10 * 20
-u^2 = -400
u = √ 400
u = 20m / s
Answer:
The speed of car A before collision is 3.5 km/h.
Explanation:
Mass of car A = 690 kg eastwards
Mass of car B = 520 kg at 74 km/h west wards
Distance, s = 6 m
coefficient of friction = 0.75
Let the speed after collision is v.
Use third equation of motion

Let the initial speed of car A is v'.
Use conservation of momentum
690 x v' - 520 x 74 = (690 + 520) x 33.8
690 v' + 38480 = 40898
v' = 3.5 km/h