Pretest 1

Select the correct order from smallest to largest.

• universe, galaxy, solar system, star

• solar system, star, galaxy, universe

• star, solar system, galaxy, universe

• star, galaxy, universe, solar system

Answer explanation

A solar system consists of at least one star and the planets that orbit it, so stars are smaller than solar systems. A galaxy contains millions of stars and is therefore bigger than a solar system. The universe contains all the galaxies (and everything else), so the universe is the largest and must come last in the list.

Which of the following is the best example of Newton’s first law (the law of inertia), which states that an object at rest stays at rest and an object in motion stays in motion at the same speed in the same direction unless acted upon by an unbalanced force?

• a train slowing to a stop as it enters the station

• the recoil of a cannon when a cannonball is fired into the air

• a skydiver who has already reached terminal velocity and is

  falling at a constant speed toward the ground

• a rocket blasting off on its way to the moon

Answer explanation

Because the skydiver has already reached terminal velocity, he is falling at a constant speed toward the ground, which means there are no unbalanced forces acting on him (his weight is balanced out by the air resistance)

What will happen if an atom gains an electron?

• Its charge would become negative.

• Its charge would become positive.

• Its charge would remain neutral.

• The charge is impossible to determine without further

  information.

Answer explanation

All atoms are neutral because they contain the same number of positively charged protons in their nucleus and negatively charged electrons in their electron shells. But if an atom gains an electron, it will no longer be neutral because the negative charge from the additional electron will change the atom into a cation (a negatively charged atom).

Which of the following is NOT a unit of weight or mass?

• ton

• gram

• kilowatt

• ounce

Which method can be used to determine whether two sisters are identical twins?

• Check to see whether their blood glucose levels are identical.

• Compare their physical appearances to see whether they look

  alike.

• Check their family history.

• Do a DNA analysis.

Answer explanation

Identical twins would have identical DNA.

Blood glucose levels vary during the day (depending upon what you eat), and they don’t give any indication of whether people are related.

Sisters can look very similar to each other, and that doesn’t necessarily mean that they’re identical twins.

The family history will be the same for all siblings.