The correct answer is D. An average city
Explanation:
A neutron star differs from others due to its massive density, this means a lot of matter is compressed in a small area. Indeed, neutron stars have a mass of around 1.4 to 2.8 times the mass of the sun. But these are considerably small as they only measure around 20 kilometers, which is the size of an average city. Additionally, neutron stars are this dense because they are the result of a regular star exploding, which leads to a super-dense core, or neutron star. In this context, the mass of a neutron star is compressed to the size of an average city.
W = m.g = weight
g = Gme/Re**2 where G= universal gravitational constant , Re= radius of the earth
me= mass of the earth
therefore it weighs 16 times less
Speed of wave = Frequency x Wavelength
so Speed = 0.7 x 9 = 6.3
remember the calculations must be done in their Basic SI units.
therefore, you have to convert 7 mm to meters which becomes 0.7 meters
Answer:
Part a)

Part b)

Explanation:
As we know that two carts are moving in opposite directions
so here total momentum of two carts must be given by vector subtraction
It is given as



Now we know that total momentum of the system is conserved here as there is no external force on this system
so the speed of the first cart when second cart was at rest is given as


