UPD Physics 71 Topics 33 ~ 36 Formative Quiz (2025-2026 First Semester)

Physics 71 offered a take-home worksheet covering topics 33 to 36 — from mechanical stress to fluid flow. It includes problem-solving exercises and has a total of 40 marks; though, 10 marks are optional.

Questions

Earth’s angular momentum. (5 points)
What is the total angular momentum of the Earth considering its rotation on its own axis and its revolution around the Sun assuming circular orbit $r = 1.5 \times 10^{11}$ [m]? Its mass is $R = 5.96 \times 10^{24}$ [kg] and radius $R = 6.38 \times 10^{6}$ [m]. Take the Earth as a solid sphere.
Disk banggaan. (5 points)
Two identical disks $I = \frac{1}{2} M R^{2}$ are rotating in the same direction about their axes with angular speeds 6.0 [rad/s] and 7.0 [rad/s]. Disk 1 is dropped from an arbitrary height and collides with disk 2. If the two disks stick together and rotates about axis O after collision, what is the angular speed of the two-disk system?
Construction site. (5 points)
A 15000 [N] crane pivots around a friction-free axle at its base and is supported by a cable making a 25-degree angle with the crane as shown. The crane is 16 [m] long and is not uniform. Its center of gravity is located at 7.0 [m] from the axle along the crane. At the upper end of the crane is a 11, 000 [N] pallet of bricks suspended using a very light cord that is 2.2 [m] long. What is the tension in the cable?
Incredible Hulk! (5 points)
Incredible Hulk stretched a copper rod, resulting to an expansion from 2.20 [m] to 2.21 [m]. What is the stress applied by Hulk on the rod? Refer to Lecture 33 for the values of elastic moduli.
Lift me up. (10 points)
The hydraulic lift is an application of Pascal’s principle that allows for the efficient lifting of heavy objects and its set-up is shown in the figure.
1. (5 points) What must be the ratio of the diameter of the vessel at the car to the diameter of the vessel where $F_{1}$ is applied so that a 1600-kg car can be lifted with a force of just $F_{1}$ = 100 [N]?
2. (5 points) Suppose that the diameter of the vessel at $F_{2}$ is $D_{2}$ = 0.40[m]. What is the gauge pressure required to lift a car with a mass of 2200 [kg]? Express your answer in atmosphere units.
So mysterious. (5 points)
An object with a mass of 2.00 [kg] is fully submerged in water. It is suspended by a string with tension 10.0 [N]. Then you fully submerge the object into an unknown liquid and the tension of the string is now 15.0 [N]. What is the density of the unknown liquid?
Siphon (5 points)
You need to siphon water from a clogged sink. The sink has an area of 0.480 [m2] and is filled to a height of 4.00 [cm]. Your siphon tube rises 50.0 [cm] above the bottom of the sink and then descends 100. [cm] to a pail as shown in the figure. The siphon tube has a diameter of 2.00 [cm]. Assuming the water enters the siphon tube with almost zero velocity, calculate its velocity (in m/s) when it enters the pail. Note that the water enters the tube from the bottom of the sink. (Hint: The answer is not zero)