In which situation is the acceleration of the car negative?
a.)the velocity of a car was 75 km/h
b.)the velocity of a car reduced from 50 km/h over one minute
c.)the velocity of a car increased from 40 km/h to 75km/h over 15 minutes
d.)the velocity of a car increased from 40 km/sh at 2: 00pm and at 4: 00pm the velocity of the car was 85 km/h

B) The velocity of the car reduced from 50k/m over one min.

Answer is: B.)The velocity of a car reduced from 50 km/h over one minute.

Ending velocity is defined as the velocity attained by a body after completing distance at certain time interval:

v(ending velocity) = v(initial velocity) + a·t.

a is acceleration attained by the body (in this examle car).

t is time (in this example one minute).

Because velocity is reduced, acceleration has negative sign.

An car average acceleration over a period of time is its change in velocity.

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms

answer carbon and three oxygen atoms;