I think to an observer outside the train, the speed of the ball will actually look like more than the speed of the train.
The De Broglie's wavelength of a particle is given by:

where
is the Planck constant
p is the momentum of the particle
In this problem, the momentum of the electron is equal to the product between its mass and its speed:

and if we substitute this into the previous equation, we find the De Broglie wavelength of the electron:

So, the answer is True.
A:True because Lithium is the lighest solid and metal and the third lightest element.
Answer:
7.55 km/s
Explanation:
The force of gravity between the Earth and the Hubble Telescope corresponds to the centripetal force that keeps the telescope in uniform circular motion around the Earth:

where
is the gravitational constant
is the mass of the telescope
is the mass of the Earth
is the distance between the telescope and the Earth's centre (given by the sum of the Earth's radius, r, and the telescope altitude, h)
v = ? is the orbital velocity of the Hubble telescope
Re-arranging the equation and substituting numbers, we find the orbital velocity:
