Expert Answers

Identify a similarity and a difference between two objects – one in static equilibrium and the other in dynamic equilibrium? Hint: think about net force and motion

If we push an object at constant velocity, how much friction acts on the object compared to our pushing force:

A) equal to the pushing force

B) greater than the pushing force

C) less than the pushing force

D) none of the above


By how much does the gravitational force between two objects decrease when the distance between their centers is doubled?

A) ½

B) ¼


D) 1/16


What happens to the acceleration of a cart if the force acting on it is quadrupled (i.e. multiplied by 4)

Tim stands in the middle of a scaffold. There is no motion. The left scale reads 450N. What is the reading on the right scale and the total weight of Tim and scaffold

A) 450N and 900N

B) 450N and 1200N

C) 400N and 850N

D) 250N and 700N

E) 1050N and 1500N

What is the force of gravity on a 2 kg mass 3.2*106 m above the Earth’s surface. The mass of the earth is 6.4*1023 kg and its radius is 6.4*106 m. Hint: the total distance between the object and the earth is from the center of the earth to the location of the object.

If two objects – one three times as heavy as the other – are in free fall, which of these statements are true:


I) The force of gravity on the heavier object is 3 times that on the lighter object

II) Their speeds are increasing at the same rate i.e. they are falling at the same rate

III) The heavier object is falling much faster than the smaller object


A) All of the above

B) none of the above

C) I and II

D) I and III

E) I only

Which of these is not a law of motion?


A) Action and reaction are equal and opposite

B) The acceleration of an object is directly proportional to the net force acting on the object

C) A body at rest or in motion continues in its state of rest or uniform motion unless a force is applied to it

D) The earth always attracts objects to its center

Define terminal velocity? Can it be reached in a vacuum? Why or why not?


What is the difference between the atomic number and the mass number of an element?


Fusion is the source of energy in the sun. What is the difference between fission and fusion?

Which of these is not an element:

A) O2

B) N2

C) He

D) Cl


What is the IUPAC name for KCl?

Hydrogen is the lightest (least heavy) element/gas. Why is it not used to fill children’s balloons? Why is helium used?

Why is there more carbon-14 in living bones than in once-living ancient bones of the same mass?


A radon atom emits a beta particle and then is irradiated with gamma rays, what is the final element? Its mass number and atomic number?

How many valence electrons are in these elements:

a) oxygen

b) boron

c) silicon

d) krypton

Which of these are true of gamma rays:

i) Its frequency is lower than ultraviolet radiation

ii) Gamma irradiation can be used to destroy harmful micro-organisms

iii) They are electromagnetic waves

iv) They can bring about genetic mutations in humans


A) i only

B) ii only

C) ii, iii and iv

D) all of the above E) none of the above

Which of these radioactive particles do not penetrate the skin?

A) Alpha particle

B) beta-particle

C) gamma rays

D) none of the above

What happens when an atom loses an electron?

A) it becomes positively charged because there are more protons than neutrons

B) it becomes positively charged because there are more protons than electrons

C)it remains neutral

D) it is a form of radioactive decay

E) none of the above

When alpha particles pick up electrons, they become _________

A) Helium gas

B) Hydrogen gas

C) Lithium

D) remain alpha particles

E) none of the above