Ans: A quantity cannot have units until it has dimensions. A quantity that has dimensions must have units. Yes a quantity have units but still be dimensionless for example,unit of angle is radian ,but it is a dimensionless quantity. A dimensionless quantity may have unit.
There would be a symbol on names of the elements that would say which state it would usually be in.
there are more metals in the periodic table of elements (currently) if that's what the second question is asking about
Full night on earth since the gravitational pull is far less compared to Jupiter's gravitational pull. Hope this helps.
Answer:
28.6260196842 m
Explanation:
Let h be the height of the building
t = Time taken by the watermelon to fall to the ground
Time taken to hear the sound is 2.5 seconds
Time taken by the sound to travel the height of the cliff = 2.5-t
Speed of sound in air = 340 m/s
For the watermelon falling

For the sound
Distance = Speed × Time

Here, distance traveled by the stone and sound is equal


The time taken to fall down is 2.4158 seconds

Height of the buidling is 28.6260196842 m