PHYS 220 - EXAM 2 QUESTIONS AND ANSWERS
When is work positive? - answers- when force and displacement are in the same
direction; angle is less than 90 degrees
When is work negative? - answers- when the force is in the opposite direction of
displacement; angle is greater than 90 degrees
What does torque indicate? - answers- rotational motion
What must be true for a system in static equilibrium? - answers- the net forces on all
parts must be zero (ex: the net force on each pulley must equal zero)
What is true of the center of mass? - answers- it is weighted towards the heavier part of
the object
Cm = (mx + mx + mx...) / (m + m + m...)
Positive angular momentum - answers- counterclockwise
Negative angular momentum - answers- clockwise
When is torque positive? - answers- if force would cause system to rotate
counterclockwise
Can kinetic energy be negative? - answers- no; however, the change in kinetic energy
can be negative
What is the minimum height something is needed to be dropped from? - answers-
2.5(r) where r is the radius of the loop
If something rotates at constant speed, what is its angular acceleration? - answers- 0
rad/s^2
A block of large or small volume will make a scale (holding a flask of water) reading
change how? - answers- larger volume will increase the scale reading; smaller volume
will decrease the scale reading
-this is because there is a greater buoyant force exerted on the object with greater
volume (pvg)
What is true of mass in an isolated system? - answers- it is a conserved quantity; it
does not change
What components does momentum have? - answers- x and y components
What does the area under a force vs time graph yield? - answers- the impulse
When is work positive? - answers- when force and displacement are in the same
direction; angle is less than 90 degrees
When is work negative? - answers- when the force is in the opposite direction of
displacement; angle is greater than 90 degrees
What does torque indicate? - answers- rotational motion
What must be true for a system in static equilibrium? - answers- the net forces on all
parts must be zero (ex: the net force on each pulley must equal zero)
What is true of the center of mass? - answers- it is weighted towards the heavier part of
the object
Cm = (mx + mx + mx...) / (m + m + m...)
Positive angular momentum - answers- counterclockwise
Negative angular momentum - answers- clockwise
When is torque positive? - answers- if force would cause system to rotate
counterclockwise
Can kinetic energy be negative? - answers- no; however, the change in kinetic energy
can be negative
What is the minimum height something is needed to be dropped from? - answers-
2.5(r) where r is the radius of the loop
If something rotates at constant speed, what is its angular acceleration? - answers- 0
rad/s^2
A block of large or small volume will make a scale (holding a flask of water) reading
change how? - answers- larger volume will increase the scale reading; smaller volume
will decrease the scale reading
-this is because there is a greater buoyant force exerted on the object with greater
volume (pvg)
What is true of mass in an isolated system? - answers- it is a conserved quantity; it
does not change
What components does momentum have? - answers- x and y components
What does the area under a force vs time graph yield? - answers- the impulse
