## Posts in category Featured

# Relativity student exam time

Spacecraft I, containing students taking a physics exam, approaches the Earth with a speed of 0.7c (relative to the Earth), while spacecraft II, containing professors proctoring the exam, moves at 0.2c (relative to the Earth) directly toward the students. The professors stop the exam after 88.0 min have passed [...]

# Space ship landing craft

Questions
A spaceship traveling at 0.540c toward the Earth launches a landing craft. The landing craft travels in the same direction with a speed of 0.880c relative to the mother ship. As measured on the Earth, the spaceship is 0.280 ly from the Earth when the landing craft is launched.
(a) What spee [...]

# Siphon Phyiscs Problem

A siphon is used to drain water from a tank with a steady frictionless flow.
See the diagram for the set up.
We can use Bernoulli equation to solve for the v. Here we can assume that the cross section area of the tube is much smaller than that of the beaker so we can treat the velocity that the water level drops in the beaker to b [...]

# Physics of Hydraulic Brake System

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Consider a hydraulic brake system as shown below. The area of the piston in the master cylinder connected to the foot paddel is 1.8 cm2. The area of the piston connected to the brake shoe is 6.4 cm2. The kinetic frictional coefficient between shoe and wheel drum is 0.50. If the wheel's [...]

# U-tube Pressure and Bernoulli Equatio...

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Question: A U-tube open at both ends is partially filled with water. Oil having a density of 840 kg/m3 is then poured into the right arm and forms a column L = 4.68 cm high (Figure b).
(a) Determine the difference h in the heights of the two liquid surfaces.
Answer: To show more clearly how to set up the locations for c [...]

# Answered: HW 10 Question 9

More Physics Homework Help at LeiAcademy.
The blocks are going to slide with acceleration to the right and down the ramp.
Do free body diagrams for the two blocks and the pulley. Define the positive direction being clock wise for the rotation and towards right and down the ramp.
For block 1, you would have 4 forces with ||N_1=m_1g|| and ||f_ [...]

# Answered: Calculating Rotational Kine...

Set the vertically standing to be initial position and horizontal to be the final position. Use energy conservation. Consider the change of potential energy: For the ball, its center of mass falls ||l+\frac d 2||. For the rod, its center of mass falls ||\frac l 2||. All these changes goes into the rotational kinetic energy.
Set y=0 at t [...]

# Answered: HW 9 Motorcycle lifting

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Draw a careful diagram to illustrate what is happening when the front wheel just lifted off the ground (touching but no forces). Label all the forces and useful parameters. Carefully observe where the different forces are applied so you can figure out the torques. Identify the center of mass clearly a [...]

# Answered: HW 9 Problem 6

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Part1: If the pulley is uniform, then it can be considered as a uniform disk, which has ||I=\frac {1}{2}mR^2||.
Part2: Based on the time and distance it falls, you can find its actual acceleration as: $$\Delta y=V_{y0} \Delta t+\frac 1 2 a\Delta t^2.$$
Plug in the g [...]

# Answered: HW 9 Problem 10, Trimmer ro...

More Physics Homework Help at LeiAcademy.
The key to solve this question is to calculate the moment of inertia of this trimmer. There are two components, one is the wire spool and the other is the plastic wire sticking out from the spool. We can use the following diagram to show how the trimmer can be considered in terms of components of [...]