Hi there!
Assuming you're asking about the solar system, there are nine planets. But, if you're wanting to know about the universe, there are trillions and trillions of planets (most of which we haven't yet discovered).
Hope this helps!
Answer:
0.465 kgm/s
Explanation:
Given that
Mass of the cart A, m1 = 450 g
Speed of the cart A, v1 = 0.85 m/s
Mass of the cart B, m2 = 300 g
Speed of the cart B, v2 = 1.12 m/s
Now, using the law of conservation of momentum.
It is worthy of note that our cart B is moving in opposite directions to A
m1v1 + m2v2 =
(450 * 0.85) - (300 * 1.12) =
382.5 - 336 =
46.5 gm/s
If we convert to kg, we have
46.5 / 100 = 0.465 kgm/s
Thus, the total momentum of the system is 0.465 kgm/s
about 5 watts (5W) of power