Q1) Answer all Multiple Choice questions. i) Newton’s 1st law is: A. PHYSICALLY INDEPENDENT of the…

Q1) Answer all Multiple Choice questions.
i) Newton’s 1st law is:
A. PHYSICALLY INDEPENDENT of the other two laws
of motion and CANNOT be dispensed with as an axiom
of Newtonian physics.
B. PHYSICALLY INDEPENDENT of the other two laws
of motion, but nonetheless it CAN be dispensed
with as an axiom of Newtonian physics.
C. Actually a SPECIAL CASE of the 2ND LAW. The
case when the net force is zero. Therefore, logically we need only
two laws of motion. Perhaps for clarity Newton formulated his
explicit 1st law and perhaps for the same reason physicists have
retained it.
D. Actually a SPECIAL CASE of the 3RD LAW. The
case when the net force is zero. Therefore, logically we need only
two laws of motion. Perhaps for clarity Newton formulated his
explicit 1st law and perhaps for the same reason physicists have
retained it.
E. is INCORRECT but is kept in the books for
historical reasons.
ii) What is the approximate mass of a woman who weighs
500N? What is gravitational force that Earth exerts on her. After
she jumps UPWARD from a diving board, what is her acceleration in
the absence of air drag?
N, and 9.8m/s2 downward once she starts moving downward, but ZERO
before that.
B. About 50 kg, 50 N,
and 9.8m/s2 downward once she starts moving downward, but ZERO
before that.
C. About 50 kg, 50 N,
and 9.8m/s2 downward at ALL times.
and 9.8m/s2 downward at ALL times
E. None of these
questions can be answered with the given information.

iii) If Newton’s 3rd law is true, why then does anything
accelerate at all?
A. The equal and opposite forces DO NOT have to
be on the same body.
B. The equal and opposite forces DO have to be
on the same body.
C. Nothing moves at all as Parmenides argued in
the 5th century BC. Motion is but seeming. Anyway Parmenides seems
to have been a pretty smart guy since he’s credited with the
spherical Earth theory and the discovery that the Moon shines by
reflected light.
D. Acceleration has nothing do with forces.
E. Forces have nothing do with
acceleration.
iv) From here on in this course, a key thing to remember
(to recite to yourself) when faced with any force problem is that
Newton’s 2nd law ()
is:
A. ALWAYS VALID. And it is a VECTOR equation,
and so is always VALID component by component. And
is the VECTOR sum of all forces acting on the body of mass m. It
is not any particular force. If all the forces sum to zero
vectorially,
= 0. If you are given the acceleration, then you can
often use
to solve for an unknown force.
B. ALWAYS VALID. And it is a SCALAR equation.
And
is the SCALAR sum of all forces acting on the body of mass m. It
is not any particular force. If all the forces sum to
zero,
= 0. If you are given the acceleration, then you can often use

to solve for an unknown force.
C. ONLY VALID when there is a NON-ZERO net
force. Because the 2nd law is a VECTOR equation, it is valid (when
it is valid) component by component. And
is the VECTOR sum of all forces acting on the body of mass m. It
is not any particular force. If you are given the acceleration,
then you can often use
to solve for an unknown force.
D. ALWAYS INVALID.
E. NEVER VALID
v) The force of gravity reaches out across space and
pulls on each bit of your body independently of every other bit. We
call a force like this a FIELD FORCE or a BODY FORCE. Why don’t you
accelerate downward, except when off the ground?

The GROUND FORCE reaches out across space and
pushes upward on each bit of your body independently of every other
bit. The ground force is also a FIELD FORCE
The ground exerts a force on the soles of your feet and the
soles of your feet on the next layer of your body and the next
layer of your body on the next layer of your body and so on until
the top of your head. Each layer pushes up with only enough force
to balance the gravity force on the mass above. The ground force
and the forces exerted by the layers of our bodies are
CONTACT FORCES. A CONTACT FORCE
acts over a very short range: so short that if the distance between
the two objects exerting equal and opposite contact forces on each
other is more than microscopic there is no contact force at
all.
Since you are always off the ground, the question has no
Since you are always off the ground, the question is
In orbit, you don’t accelerate downward, and you are certainly
off the ground. So being on the ground may have nothing to do with
why you don’t accelerate downward.

vi) Forces can cause accelerations relative to inertial
frames or cancel other forces. Another manifestation (which
actually follows from their property of causing acceleration) is
that they can cause:
A. velocity (without causing
acceleration)
B. mass
C. bodies to distort: i.e., flex,
compress, stretch, etc
D. bodies to live
E. bodies to rule

vii) A book sits at rest on a table. There action force
that follows from Newton’s 3rd law to the gravitational force of
the Earth on the book is the:
A. gravitational force of the book on
the Earth.
B. normal (i.e., perpendicular upward)
force of the table on the book.
C. table friction force on the
book.
D. book friction force on the
table.
E. book normal force on the table.
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