Physics 7. Homework # 8
Due:
5/24
1) What is the equivalence principle?
What does it imply when considering the motion of objects under the influence
of gravity?
a) The equivalence principle states
that all inertial observers are equivalent, and it implies that gravity is
absent in all inertial frames
b) The equivalence principle states
that inertial and gravitational masses are identical, it implies that all
objects experience the same acceleration under gravity
c) The equivalence principle states
that gravitational and inertial masses are identical only in inertial reference frames; and it
implies that gravitational acceleration is proportional to the square of the
mass
d) The equivalence principle states
that speed of light is absolute, and it implies that mass and energy are
equivalent
2) Alma
and Omar are twins born on the surface of a very massive planet. When they were
25 years old
a) He was also 50 years old
b) He was younger than
c) He was older than
d) He is shortened permanently
because of relativistic length contraction
3) Why
a black hole is called that way because,
a) Its escape velocity is larger than
c, so light cannot escape its
vicinity
b) It converts all its energy
into matter
c) It emits only X-rays, so it
looks black to our eyes
d) It emits only microwave
radiation, so it looks black to our eyes
4) When
we see astronauts inside the space shuttle they appear weightless. Is there a
force acting on the?
a) No, because there is no
gravity in space
b) Yes their weightlessness is an
optical illusion
c) Yes, but it is countered by
the sun’s gravitational attraction
d) Yes, the Earth’s gravity acts
on them (that is why they keep in orbit and not move at constant speed in a
straight line), however, astronauts and shuttle are
accelerated in precisely the same way so with respect to the shuttle
the astronauts do not accelerate.