 # College Physics Questions and Answers

Recent questions in Physics Jazlyn Raymond 2022-04-06

## I am a bit confused regarding the nuclear fusion that occurs during star formation. For example, suppose there is a huge hydrogen cloud. It gets more mass and therefore pulls in more and more hydrogen, but it could just do this endlessly and get endlessly big. What causes it to stop growing? Is it because of the heat generated by the huge mass? Jordon Haley 2022-04-06

## If you have 2 flashlights, one facing North and one facing South, how fast are the photons (or lightbeams) from both flashlights moving away from one another?Just adding speeds would yield 2C, but that's not possible as far as I know.The reference frame here would be the place where the flashlights are and/or .The beams relative to one another. Ashley Fritz 2022-04-06

## A ball is thrown at a relative velocity of in $+ve$ $x-$ direction in a rocket in gravity free space. The rocket has a constant acceleration of $2m/{s}^{2}$ also in $+ve$ $x-$ direction.Whether uniform acceleration equations of motion would apply in above case when using the rocket as a frame of reference. As an example, would the equation $s=ut+.5a{t}^{2}$ apply if rocket is taken as frame of reference? Jayla Faulkner 2022-04-06

## Is Planck temperature really the highest temperature?Actually I was learning about Wien's displacement law. It states that$\lambda T=2.898×{10}^{-3}mK$This is actually a part of Planck's law where the Planck's constant originated.Now Planck's temperature is given as${T}_{p}=\sqrt{\frac{h{c}^{5}}{2\pi G{k}_{b}^{2}}}=1.416×{10}^{32}K$Now Planck's length is $1.616×{10}^{-35}m$Now since the smallest possible wavelength is Planck's length, we can say wavelength of the electromagnetic radiation is Planck's length (Assume the energy doesn't create a black hole).Now according to Wien's displacement law,${l}_{p}T=2.898×{10}^{-3}mK$Now solving this we get $1.79×{10}^{32}K$, which is higher than the actual Planck's temperature.Since this displacement law is completely derived from Planck's law, it bit frustrated me. I'm a bit confused. Is it the limit of the displacement law or my flaw?Please rectify this.(Sorry if I made any mistake. I'm new to this one. Please explain my mistake. I'm glad to hear that.) Dennis Montoya 2022-04-06

## What is the half life of Uranium 234? Adelyn Rodriguez 2022-04-06

## If an observer were to rotate around a point at near light speeds, what sort of length contraction would he observe the universe undergo? quiquenobi2v6 2021-12-15

## An open tank has a vertical partition and on one side contains gasoline with a density $p=700\frac{kg}{{m}^{3}}$ at a depth of 4m. Arectangular gate that is 4 m high and 2 m wide and hinged at one end is located in the partition. Water is slowly added to the empty side of the tank. At what depth, h, will the gate start to open? alka8q7 2021-11-17

## The air in a bicycle tire is bubbled through water and collected at ${25}^{\circ }C$. If the total volume of gas collected is 5.45 L at a temperature of ${25}^{\circ }C$ and a pressure of 745 torr, how many moles of gas were in the bicycle tire? Nannie Mack 2021-05-04

## When a gas is taken from a to c along the curved path in the figure (Figure 1) , the work done by the gas is W = -40 J and the heat added to the gas is Q = -140 J . Along path abc, the work done by the gas is W = -50 J . (That is, 50 J of work is done on the gas.) I keep on missing Part D. The answer for part D is not -150,150,-155,108,105( was close but it said not quite check calculations) Part A What is Q for path abc? Express your answer to two significant figures and include the appropriate units. Part B f Pc=1/2Pb, what is W for path cda? Express your answer to two significant figures and include the appropriate units. Part C What is Q for path cda? Express your answer to two significant figures and include the appropriate units. Part D What is Ua?Uc? Express your answer to two significant figures and include the appropriate units. Part E If Ud?Uc=42J, what is Q for path da? Express your answer to two significant figures and include the appropriate units. Falak Kinney 2021-04-06

## Part A Suppose a uniform slender rod has length L and mass m. The moment of inertia of the rod about about an axis that is perpendicular to the rod and that  Cheyanne Leigh 2021-04-04

## Water at a pressure of $3.00×{10}^{5}$ Pa flows through a horizontal pipe at a speed of 1.00 m/s. the pipe narrows to 1/4 its original diameter. Find the following: A. The flow speed in the narrow section B. the pressure in the narrow section smileycellist2 2021-03-23

## A 45-g piece of ice at 0 degree C is added to a sample of water at 8 degrees C. All of the ice melts and the temperature of the water decreases to 0 degree C. How many grams of water were there in the sample? preprekomW 2021-01-13

## An ice cube tray of negligible mass contains 0.315 kg of water at ${17.7}^{\circ }$. How much heat must be removed to cool the water to ${0.0}^{\circ }$ and freeze it? beljuA 2021-01-13

## A cubic block of wood, 10.0 cm on each side, floats at the interface between oil and water with is lower surface 1.50 cm below the interface. The density of oil is 790 kg/m(cubic). a) what is the gauge pressure on the upper surface of the block? b) what is the gauge pressure on the lower surface of the block? c) what is the mass and density of the block? Anish Buchanan 2020-12-30 Tammy Todd 2020-10-18