Download Physics 50 Sample Midterm Exam #1

Physics 50 Sample Midterm Exam #1
(26 points)
by Todd Sauke
Question #1.
A train starts from rest (at initial position = 0) and accelerates uniformly, until it has traveled 3.3
km and acquired a velocity of 48 m/s. The train then moves at a constant velocity of 48 m/s for
430 s. The train then decelerates uniformly at 0.065 m/s2 until it is brought to a halt. We want to
determine the acceleration during the first 3.3 km of travel. Fill in the table below with the
values of the kinematic variables for the problem involving the first 3.3 km of travel. Write
"target" in the table to indicate the target variable.
|
x
|
x0
|
vx
|
v0x
|
ax
|
t
|
1 point
Write the constant-acceleration equation (from the study guide) involving the given kinematic
variables and the target variable.
_________________________________
1 point
Solve the equation for the target variable. (Make sure to use SI units consistently)
acceleration= _______________
1 point
__________________
include units (½ point)
How much farther does the train travel during the 430 s of constant velocity motion?
__________________ ____________
1 point
(units) ½ point
Now we want to determine the total distance traveled by the train once it has stopped moving.
Fill in the table below with the values of the kinematic variables for the problem involving the
final (decelerated) travel. Write "target" in the table to indicate the target variable.
|
x
|
x0
|
vx
|
v0x
|
ax
|
t
|
1 point
What is the total distance traveled by the train?
________________________ ___________
1 point
(include units to get full credit)
Question #2.
A racquetball strikes a wall with a speed of 30 m/s and rebounds with a speed of 26 m/s. The
collision takes 20 ms (milliseconds). We want to determine the magnitude of the average
acceleration of the ball during the collision.
Write the equation (from the study guide) for finding the average acceleration.
__________________________________
1 point
What is the magnitude of the average acceleration of the ball during the collision?
________________________________________
2 points
_________________
include units to get full credit
Question #3.
A projectile is fired at time t = 0.0s, from point 0 at the edge of a cliff, with initial velocity
components of v0x = 80 m/s and v0y = 600 m/s The projectile rises, then falls into the sea at point
P, as shown in the figure. The time of flight of the projectile is 150.0 s. We want to determine
the magnitude of the velocity of the projectile at time t = 15.0 s (in mid-flight). Remember that
for projectile motion, the x and y motions are independent, with y acceleration given by gravity
and x acceleration zero. First let's figure out the vertical velocity of the projectile at t = 15.0 s.
Fill in the table below with the values of the y-axis (vertical) kinematic variables relevant to the
problem. Write "target" in the table to indicate the target variable.
|
y
|
y0
|
vy
|
v0y
|
ay
|
t
|
1 point
Write the equation involving the appropriate kinematic variables.
__________________________________
1 point
Solve for the vertical velocity of the projectile at t = 15.0 s.
What is the horizontal velocity of the projectile at t = 15.0 s?
vy(15) = ____________m/s
1 point
vx(15) = ____________m/s
1 point
What is the magnitude of the velocity of the projectile at time t = 15.0 s?
______________m/s
1 point
Question #4.
A plastic ball in a liquid is acted upon by its weight and by a buoyant force. The weight of the
ball is 2.7 N. The buoyant force has a magnitude of 7.1 N and acts vertically upward. At a given
instant, the ball is released from rest. We want to determine the acceleration of the ball at that
instant, (including direction). Make a free body diagram of the ball, including all of the things
that should be in a good free body diagram.
Write the equation for determining the
acceleration of the ball when released.
______________________________
1 point
What is the acceleration of the ball?
___________________________________
Free body diagram, 2 points
____________________________m/s2
1 point
Question #5.
A block is on a horizontal frictionless table, on earth. The block accelerates at 8.4 m/s2 when a
90 N horizontal force is applied to it. Now the block and table are set up on the moon. The
acceleration due to gravity at the surface of the moon is 1.62 m/s2. A horizontal force of 45 N is
applied to the block when it is on the moon. We want to determine the acceleration imparted to
the block. Make a free body diagram of the block when it is on earth, including all of the things
that should be in a good free body diagram.
Write the equation relating the horizontal
acceleration, mass and forces on the block
when it is on the earth.
______________________________
½ point
What is the mass of the block?
___________________________________
____________________________kg
Free body diagram (earth), 1 point
1 point
Make a free body diagram of the block when it is on the moon, including all of the things that
should be in a good free body diagram.
Write the equation relating the horizontal
acceleration, mass and forces on the block
when it is on the moon.
______________________________
½ point
What is the acceleration of the block?
___________________________________
Free body diagram (moon), 1 point
____________________________m/s2
1 point
Question 6. (2 points)
Two football teams, the Raiders and the Jets, are engaged in a tug-of-war. The Raiders are
pulling with a force of 5,000 N. Which of the following is an accurate statement?
A) The Jets are pulling with a force of more than 5,000 N if they are winning, i.e. pulling
the Raiders in the direction toward the Mets.
B)
The Jets are pulling with a force of 5,000 N.
C)
The tension in the rope is 10,000 N.
D) The tension in the rope depends on whether or not the teams are in equilibrium.
E) None of these statements is true.