Scalar quantity which is the magnitude of velocity.

learn more… | top users | synonyms

0
votes
2answers
25 views

How to calculate the acceleration, if the mass-center is not on the force-vector's line (2D)

In a 2D plane there is an object, whose center of mass is at the $P$ point. The mass of the object is $m$. We apply a force $\vec F$ at the point $A$. If the center of mass is on the line, defined ...
0
votes
2answers
36 views

How to calculate the maximum speed of an object?

There is a spaceship, whose mass is $100 \, \mathrm{kg}$. The thrust of its rocket is $300 \, \mathrm{N}$. How is it possible to calculate the maximal speed that the spaceship can reach, and the time ...
1
vote
1answer
48 views

The Energy Equation

I've been studying the energy equation in relativistic motion $E= \frac{mc^2}{\sqrt{1-v^2/c^2}}$, which can be expanded as $$E = mc^2 + \frac{1}{2} mv^2\text{ + some other terms.}$$ I'm curious ...
-1
votes
2answers
44 views

can time dilation be used to determine if an object is moving

I know that movement is only relative to another object, but as you move faster you also experience time dilation, correct? So if one body is moving faster then it should have a dilation of time, ...
2
votes
2answers
49 views

Submerged water jet

I am trying to calculate at what pressure and speed water from a high pressure water jet will hit an object 100 millimeters away from the nozzle opening, but i can't figure it out. The nozzle will ...
0
votes
1answer
24 views

Would a bullet damage a piece of metal the same as a pointy stick?

If you used a materials that would offer zero bending or dulling (the bullet/ pointy stick), would a 10 g bullet traveling at 1000 m/s with a surface area of 1 mm squared damage a piece of metal the ...
5
votes
1answer
649 views

Liquid wave faster than sound in the above gas: possibility implications

I recently heard that tsunamis (meaning "harbour wave") can travel over 800 kilometres per hour (500 mph), not so far from the speed of sound in the air. May it happen, in general, that a wave in a ...
1
vote
1answer
54 views

Can Doppler Shift be used to calculate speed of an observed object?

Thanks for looking. Just musing over an idea this afternoon: if I had a radio controlled plane, I could obviously calculate its airspeed based on pings and the known speed of sound if it was ...
0
votes
0answers
19 views

Force by torque or force by speed with make the body jump?

I have a small object made of plastic weighing 3kg and I want to make it jump with the help of a dc motor and a plastic rod attached to it (4 such motor with rod are attached on the object at 4 ...
4
votes
2answers
79 views

Does an object travelling at the speed of light cast a shadow? [closed]

Asked by my 8yo today and left me scratching my head.
1
vote
1answer
58 views

Does travelling towards something at relativistic speed cause it to appear to speed up?

If one were to travel towards a giant TV floating in space, at a fraction of the speed of light, would a video playing on the TV appear to play faster? I'm guessing the answer is no. From what I ...
8
votes
3answers
2k views

Is there a maximum energy for a relativistic particle?

So I was told today that the Standard Model breaks down at really, really high energies. The lecturer mentioned particles such as electrons hypothetically having energies equivalent to that of entire ...
52
votes
4answers
13k views

Can a tomato pierce a hole in a steel plate if only the tomato is travelling fast enough?

A tomato is travelling very fast towards a 1 cm thick steel plate. Let's say this happened in a vacuum, so that the air resistance wouldn't rip the tomato apart before it even hit the steel plate. ...
0
votes
2answers
108 views

How fast does the water have to go? [closed]

I have a pot of water. There is a one-way filter at the bottom right: How fast would the water have to be travelling to go into the tank via the one-way filter? Also, I would like to have some ...
-5
votes
1answer
60 views

If a car is travelling faster than the speed of light, do the headlights still work? [closed]

If a car is travelling faster than the speed of light, do the headlights still work? If you can help because i really need to know i am going on a trip with my car tomorrow!
1
vote
2answers
86 views

Can light projection on a wall travel faster than the speed of light? [duplicate]

If I project a flashlight beam on a wall and turn the source, the projection (as seen on the wall) is seen moving along the direction of the turn with some speed. If I have projected it on a gigantic ...
0
votes
1answer
28 views

How to calculate the diameter of a moving circle from afar while lacking and knowing some information?

Let's say there is a solid wood wheel with two tires attached at the bottom travelling on a level road towards me while facing me width-wise (as in, the side of it from which you can see its ...
-2
votes
1answer
41 views

Can motion be characterized without time as independent variable? [closed]

I was just thinking about speed = distance/time which relatively describes how fast something is moving wrt some still object. So if by some wishful thinking or some coordinate system I remove the ...
2
votes
2answers
72 views

Why can't we use this method to achieve extreme speeds?

Turn an axle with diameter 1 inch at 1 mile per hour, and an attached wheel with diameter 5 inches will spin at 5 miles per hour. Why can't we apply this principle on a much bigger scale? Say you put ...
1
vote
1answer
35 views

Can absolute speed be determined by an object's mass?

It's been said that nobody can actually know how fast the Earth is moving through space, because a reference point is needed to determine absolute velocity. But if mass increases as speed increases, ...
3
votes
0answers
12 views

Why is this result wrong for finding speed of a neutron in relation to deBroglie wavelength [duplicate]

So given a deBroglie wavelength 1.8nm and the equations E=hf and E=1/2mv^2 you can get v = 2h/m*(1.8*10^-9) but this is 2 times the expected value. Wherever I look online people use the momentum p ...
1
vote
1answer
34 views

How fast does a long object bent at the center need to be travelling in order to boomerang?

At an angle, of course. Standard pressure, average temperature, and calm wind. Bonus question: Can an object that is not bent boomerang at all? If yes, how different would the equations for this ...
3
votes
0answers
57 views

Faster alternative to travel to any location in the west? [closed]

Suppose one needs to travel to Somalia from Indonesia(which are approximately at a distance of $4000$ miles from each other on the line of equator). To accomplish this task, I suggest the following ...
1
vote
0answers
40 views

Impossible? Or not? [closed]

If the universe is expanding at light speed, and you stand on the edge moving out, if you look across the universe, then you will see twice the light speed, why is that?
-1
votes
1answer
76 views

Field of view from travelling at (almost) the speed of light?

As we go faster, our field of view increases, but would happen if we travelled at (almost) the speed of light? My questions: Can we see a 360 degree view while travelling at (almost) the speed of ...
2
votes
1answer
36 views

Power vs. Speed - Indoor rowing

In the sport of indoor rowing (and probably others) I know that to double your speed you must increase your power output by a factor of eight. I am wondering why this is the case. The indoor rower ...
2
votes
0answers
19 views

Why did they use two separate vectors to calculate the magnitude and angle of the initial velocity?

The question/solution are on the attached images. (It's dealing with projectile motion) I already understand how to work out part a, but I'm having trouble understanding why they used the final ...
0
votes
1answer
45 views

Calculating speed of an object at the bottom of a curved slope? [closed]

Say you had a slope and it was like a ski slope that started shallow, got steeper and shallow again, and you knew that the top of the slope was a certain height vertically upwards from the bottom of ...
0
votes
1answer
74 views

How should speed be expressed in Frenet-Serret frame of reference? [closed]

I'm looking for the equation of motion of the ball on a vertical plane with a cylindrical profile. I guess that means I have to use the frame of reference of Frenet-Serret here. Why is the speed of ...
0
votes
0answers
19 views

Time taken to cover a point object in a circular region

I'm assuming a finite width rotating beam with increasing width as it gets closer to the circular edge. I'm trying to find the time it takes the beam to cross a point object at some distance from the ...
0
votes
1answer
72 views

What is meant by 'Phase velocity is $c^2/v$' [closed]

Is phase velocity $c^2/v$ or $v/2$? Is there only one phase velocity as indicated by the above formula? If yes then why is wavepacket said to be superposition of 'waves' whose velocity is termed as ...
0
votes
3answers
119 views

Why is the speed of sound lower at higher altitudes?

At sea level the speed of sound is 760mph, but at altitudes like the Concorde would fly at (55,000ft) the sound barrier is at 660mph, so 1000th slower. Does it have to do with lower pressure?
1
vote
2answers
189 views

At What Point Does Mass Cease to Matter?

I know very little about physics so I naturally have a lot of simple minded questions. Assuming I am piloting a rocket and want to obtain the fastest speed possible. At what point does mass more ...
1
vote
2answers
80 views

Speed and multiple images

Why an object (or something else) create multiple images of itself when it is moving fast? An earphone spinning in circle for example.
-2
votes
1answer
65 views

Objective velocity (Relativity theory) [closed]

Suppose that I have a velocity of (approximately) $c$. Then I decelerate with $c$ per hour for exactly one hour. Then I would know that I would be standing still in the end, because the decelleration ...
1
vote
1answer
85 views

Why does the wavelength gets shorter in the denser medium in refraction? [duplicate]

In the refraction, the wavelength gets shorter if it enters denser medium. Why is that happening? Is it just a phenomenon?
2
votes
1answer
53 views

Difference between escape velocity and speed [duplicate]

What is the difference between escape velocity and escape speed , is their any error if we use them interchangeably?
-1
votes
1answer
49 views

Speed Calculater [closed]

I want to make an android calculator which can calculate speed of a vehicle by using mobile sensors(accelerometer or GPS) i am interested to calculate it by using accelerometer instead of GPS is it ...
0
votes
1answer
90 views

Question about acceleration & deceleration in real world?

have searched the net and am not satisfied with any answer I have found to calculate the following:- Here is an example just for reference. Suppose I can accelerate my car from 0-100km/h in 10s. That ...
-1
votes
3answers
187 views

Can rotating disk clocked at its center at the speed of light have an outer edge that travels faster than the speed of light? [duplicate]

I have been running this through my head for a few days and I understand I am probably missing something very simple here. If a wheel is spinning the outer edge will travel at a speed that is greater ...
0
votes
1answer
46 views

Behaviour of gases in a vacuum

I have a doubt related to the behaviour of gases in a vacuum. In the following figure: The grey part is the vacuum and the green part is the gas, let the gas be Carbon Monoxide. The following are ...
1
vote
2answers
38 views

light speed broadcasts [closed]

I’m a writer. I'm working on a story. It’s sold actually, but they want some changes and I’m trying to figure out the science.. IDEA: A distant planet picks up broadcasts from Earth, so the ...
1
vote
2answers
75 views

Calculating speed of satellite in vacuum?

Satellite speed is $35\ \mathrm{km/s}$ after burn for $500\ \mathrm{ sec}$ and after some days or months this speed is reduced automatically $34$, $33$, $32$ respectively. Questions: How the ...
0
votes
3answers
93 views

How do radar speed signs work?

Everyday when I'm going back home from college, I pass by this big radar speed sign and I've noticed that it does a peculiar thing. The sign is placed on a downward slope of the street. So say I'm ...
1
vote
0answers
26 views

Escape speed or Escape Velocity? [duplicate]

Which one should be the correct term escape speed or escape velocity? In one book it is given Speed whereas in another its velocity.
1
vote
0answers
75 views

Electric skateboard speed calculations [closed]

I have a slight issue figuring out how the mass of person (≈110kg) will affect the theoretical top speed achieved. Below are the details: (1) Motor kv : 270 kV (2) Batteries: 19.8V Motor Speed: ...
0
votes
2answers
140 views

What happens if a motorcycle going at 50mph crashes head into a car going at 60mph? [closed]

I wonder if a motorcycle (going at 50mph) crashes into a car (going 60mph), what is the damage that motorcycle will experience? Here's a diagram that shows what I've in mind: ...
1
vote
3answers
55 views

What prevents me to accelerate an object to near light speed in space?

As far my limited knowledge go, things in space aren't slow down unless something interferes with them, so what prevents me to build a spaceship powered by nuclear power that will keep accelerating ...
1
vote
1answer
126 views

How fast would you have to run to create a mirror image?

So I was watching The Flash and in the most recent episode he runs so fast that he is able to create a mirror image of himself so that it looks like there is more of him than there actually is. So I ...
1
vote
3answers
72 views

Initial speed in homework problem [closed]

This is a homework question. I tried to solve it, but failed. I had to translate this question, so please forgive me if it is poorly worded. In this question you can ignore the atmospheric ...