Answer:
Explanation:
Given
Initial velocity of first billiard ball 
Initial velocity of second billiard ball 
After collision first ball comes to rest
suppose m is the mass of both the balls
Conserving momentum to get the speed of second ball after collision
Initial momentum 
Final momentum 
where
and
are the speed of first and second ball respectively



thus speed of second ball after collision is equal to speed of first ball before collision
Explanation:
It is given that, the metal with the highest melting temperature is tungsten which melts at around 3400 K, T = 3400 K
We need to find the wavelength of the peak of the black body distribution for this temperature. It can be calculated using Wein's displacement law as :

k is the constant,



or

The wavelength of infrared is from 700 nm to 1 mm. So, the lies in infrared region of the spectrum. Hence, this is the required solution.
Answer:
d. observing sunspots on the Sun and mountains on the Moon
Explanation:
Galileo was an Italian Physicist and Astronomer and is regarded as the father of modern Physics.
It was previously believed that the objects in the heavens such as the sun, moon and stars were perfect and rough till he observed sunspots on the sun and mountains on the moon which indicates the surface of the moon is rough with mountains and craters.
2 I hope it help sorry if it is wrong
The answer is a
Hope this helps!