Answer:
a)
, b) 
Explanation:
a) The equation for vertical velocity is obtained by deriving the function with respect to time:

The velocities at given instants are, respectivelly:


Answer:
The number of crates is 84580.
Explanation:
mass, m = 30 kg
height, h = 0.9 mm
Power, P = 0.5 hp = 0.5 x 746 W = 373 W
time, t = 1 minute = 60 s
Let the number of crates is n.
Power is given by the rate of doing work.

C. It depends on the medium
Answer:
no.
Explanation:
because the mass of an object never changes.
<u>Answer:</u> The correct answer is two electrons are shared between each hydrogen atom and the carbon atom bonded to it, and four electrons are shared between the carbon atoms.
<u>Explanation:</u>
Ethylene is a compound given by the chemical formula
.
The bond present between hydrogen and carbon atoms or carbon and carbon atoms are covalent bonds. A covalent bond is formed by the sharing of electrons between the atoms combining.
A double bond is present between carbon and carbon atoms. So 2 pairs of electrons are shared which means in total of 4 electrons are shared.
Bond present between hydrogen and carbon atoms are single bonds. So, a pair of electrons is shared which means that in total of 2 electrons are shared.
Hence, the correct answer is two electrons are shared between each hydrogen atom and the carbon atom bonded to it, and four electrons are shared between the carbon atoms.