AP Physics Semester 1 MC Answers Study Guide Graded A
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AP Physics Semester 1 MC + Answers Study Guide Graded A+
An object is moving to the right with speed vi when a force of magnitude F is exerted on it. In which of
the following situations is the object's direction of motion changing & kinetic energy decreasing at the
instant shown below:
A ball ...
AP Physics Semester 1 MC + Answers Study
Guide Graded A+
1). An object is moving to the right with speed vi when a force of magnitude f is exerted on it. in
which of
the following situations is the object's direction of motion changing & kinetic energy
decreasing at the
instant shown below:
Ans: Vi to the right
F up and to the left
2). A ball is suspended by a lightweight string, as shown above. the ball is displaced to position
1 and
released. the four labeled positions are evenly spaced along the arc of the ball's motion.
between
which adjacent pairs of positions is the change in kinetic energy of the ball greatest:
Ans: 1 to 2 since it drops the farthest vertically
3). A bus is initially traveling north at a constant speed, as shown above. as the bus starts to
make a left
turn without changing speed, a passenger notices that a box on the floor starts sliding
toward the right
side of the bus. which of the following top views of the box, when correctly labeled, would
best
represent all of the horizontal forces exerted on the box as it starts sliding:
Ans: only friction to the left
4). Three identical blocks (above) each take a different path from a height h to the ground.
block a is
released from rest and falls vertically. block b is released from rest and slides down a
frictionless incline.
block c is projected horizontally with an initial speed v (5 & 6).
Ans:
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, 5). Which block takes the longest time to reach the ground
Ans: the one going down the ramp since it has a=gsinθ instead of just g
6). Which block has the greatest speed just before hitting the ground:
Ans: the one launched horizontally since it has a v0
7). A ball is dropped from rest and falls to the floor. the initial gravitational potential energy of
the ball earth-floor system is 10j. the ball then bounces back up to a height where the
gravitational potential energy is 7j. what was the mechanical energy of the ball-earth-floor
system the instant the ball left the floor:
Ans: 7 (on the way up the K at bottom must be the same as the Ug at top)
8). A 50n box is at rest on a horizontal surface. the coefficient of static friction between the box
and the surface is 0.5, and the coefficient of kinetic friction is 0.3. a horizontal 20n force is
then exerted on the box. the magnitude of the acceleration of the box is most nearly:
Ans: 0
[f=.5(50)=25N; therefore; the 20N force is not enough to overcome the f (not moving)
9). Two carts, of mass 2m & m, approach each other head-on with the same speed v as shown
above. when the carts collide, they hook together. assuming positive momentum is to the
right, which of the following best represents the momentum of the cart of mass m as a
function of time before and after the collision:
Ans: below x axis then above at one third the magnitude
10). A student stands at one end of a raft floating in a pool with equally spaced marks along the
bottom, as shown above. the student and the raft have the same mass. the student walks to
the opposite end of the raft. which of the following best shows the final locations of the raft
and student relative to the marks at the bottom of the pool. assume that there is no drag
force between the raft and the water:
Ans: raft moves one back guy moves two forward
11). Cart a moves horizontally on a frictionless track. it collides and sticks to identical cart b,
which is at rest. the speed of cart a before the collision is measured to be 3.0m/s, with an
uncertainty of ±0.2m/s. students are asked to predict the speed of the carts after the
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, collision. given the uncertainty of the measurement for the speed of cart a, which of the
following is the best prediction:
Ans: find least and most it could possibly be
1.4 to 1.6
12). A lion is running at constant speed toward a gazelle that is standing still, as shown above.
after several seconds, the gazelle notices the lion and accelerates directly toward him,
hoping to pass the lion and force him to reverse direction. as the gazelle accelerates toward
and past the lion, the lion changes direction and accelerates in pursuit of the gazelle. the
lion and the gazelle eventually each reach constant but different speeds. which of the
following sets of graphs shows a reasonable representation of the velocities of the lion and
the gazelle as functions of time:
Ans: lion goes constant then up, crosses x axis, then constant
gazelle is constant at 0 then increasing then constant higher than lion
13). A spacecraft of mass 4000kg is traveling in a straight line in the positive direction. engines
can be fired so that the force exerted on the spacecraft is in the positive or negative
direction. the graph above shows data for the force during one interval. which of the
following is the best estimate of the net change in the speed of the spacecraft from time
t=0 to time t=4s:
Ans: .1 m/s
area of F vs. t is impulse in Ns
14). A rocket is continuously firing its engines as it accelerates away from earth. for the first km
of its ascent, the mass of fuel ejected is small compared to the mass of the rocket. for this
distance, which of the following indicates the changes, if any, in the kinetic energy of the
rocket, the gravitational potential energy of the earth-rocket system, and the mechanical
energy of the earth-rocket system:
Ans: KE, Ug, and system mechanical energy all increasing
15). A child slides from rest down slides a and b shown above. the slides are the same height,
and the coefficient of friction between the slides and the child is the same. which of the
following compares the change of ∆k in the kinetic energy of the child and the change ∆u in
the potential energy of the childearth system for the two slides:
a is shorter slide b is longer
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