LRA 211 Radio Physics Final exam with
answers
if an object isnt moving, no external forces act on it false, forces don't necessitate
motion
an object can move even when there is no force acting on it true. movement
doesn't require force
if a net force is acting in the y direction, then the...
LRA 211 Radio Physics Final exam with
answers
if an object isnt moving, no external forces act on it ✔✔false, forces don't necessitate
motion
an object can move even when there is no force acting on it ✔✔true. movement
doesn't require force
if a net force is acting in the y direction, then the object will move only in the y direction
✔✔false, Fx tells you nothing about y motion
at its maximum height, an object thrown straight upward has a vertical acceleration of
zero ✔✔false
it is possible for an object's velocity and acceleration to be of opposite sign at any
instant of time ✔✔true
collisions always conserve momentum ✔✔true
a normal force can be horizontal ✔✔true
collisions always conserve kinetic energy ✔✔false
collisions always conserve the total energy ✔✔true
a car accelerating uniformly from rest requires a constant power ✔✔false
a box is sitting in an elevator. in which situation is the normal force on the box the
greatest? ✔✔the normal force for a box on a level surface always has the same
magnitude
one or more external forces, large enough to be easily measured are exerted on the
wagon enclosed in the dashed box. Identify the reaction to each of these forces by
choosing all that apply ✔✔force exerted by wagon on handle to the left
in a perfectly inelastic collision between two objects, which condition necessarily
guarantees that the final energy will be zero (so that all energy is lost) ✔✔the objects
must have the same momenta but in opposite directions
A woman applies a constant horizontal force of magnitude F pushes a box of mass m
across a rough surface with a constant speed v over distance d. The woman was
supplying average power P1. What power P2 would be required if you doubled the
, force, doubled the distance,and doubled the mass m while starting with the same initial
velocity v? ✔✔P2 = 2P1
A vector A has components Ax and Ay and magnitude A. A vector of the same size but
in the opposite direction. ✔✔can be represented by -A
has a components -Ax and -Ay
has a magnitude A
has magnitude squareroot(Ax^2 + Ay^2)
An object starting at t=0 from rest at x= 0 moves to x=a where it is again at rest after a
time ta. Its average velocity for this period ✔✔is less than its maximum velocity while in
motion
At t=0 an object is at Xo. At t=t1 the object is at X1. On a graph of position vs time, the
instantaneous speed of the object at time t is given by ✔✔the tangent to the curve at t
A ball is thrown vertically upwards with speed vo, rises to some maximum height and
then falls down to the ground. Its acceleration while it is in the air (ignore air resistance)
✔✔is constant
Case 1: a ball is thrown vertically upwards with speed vo from the top of a building and
eventually hits the ground at the base of the building.
Case 2: a ball is thrown vertically downwards with speed vo from the top of the same
building. The speed of the ball as it hits the ground.. ✔✔is the same for CASE 1 and
CASE 2
The equation, x= 1/2 at^2 for the position of an object at time t is valid ✔✔only for an
initial speed that is zero
a bullet is fired with speed vo horizontally at a height of six feet across the utah salt
flats. Its speed when it hits the ground.. ✔✔is greater than v0
If an object is acceleratinog but its speed does not change ✔✔the acceleration is in a
direcion perpendicular to its velocity and it is travelling in a circle
a projectile is launched with initial speed vo from ground level, at an angle with respect
to the positive x-direction (which is horizontal; the y-axis is vertically upwards) The
projectile lands a certain horizontal distance (the range) from the launch position. If the
angle is less than 45 degrees ✔✔there is another angle with the same range
you are standing in the aisle of a bus traveling 30 miles per hour. You hold a book in
front of you and above the floor. You let go of the book. Which two laws of mostion best
explain the fact an observer on the sidewalk sees the book land on the floor by your
feet? ✔✔Newtons first and second laws of motion
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