• ### If a fly collides head-on with a railway train, the fly changes direction and must momentarily be stationary. So does it stop the train?

A fly flying towards a railway locomotive collides with its windscreen. Its direction of travel switches from one to the polar opposite. In changing its velocity from one state to the polar opposite it follows that for an instant it must have been stationary. Since the fly was in contact with the locomotive when... show more
A fly flying towards a railway locomotive collides with its windscreen. Its direction of travel switches from one to the polar opposite. In changing its velocity from one state to the polar opposite it follows that for an instant it must have been stationary. Since the fly was in contact with the locomotive when its velocity changed, did it therefore cause the locomotive to momentarily stop in its tracks?
7 answers · 6 days ago
• ### What can I do to understand my physics professor better?

I have a B I don't understand a word she says though. I have to go to other places to get the subject. If I could I wouldn't go to her class except to take tests and quizzes.
I have a B I don't understand a word she says though. I have to go to other places to get the subject. If I could I wouldn't go to her class except to take tests and quizzes.
9 answers · 1 week ago
• ### What unwanted energy transfer happens in a door hinge?

Best answer: Coverting kinetic energy into heat energy. Heat energy is most unwanted energy.
Best answer: Coverting kinetic energy into heat energy. Heat energy is most unwanted energy.
4 answers · 4 days ago
• ### A ball thrown horizontally at 26 m/s travels a horizontal distance of 51 m before hitting the ground.?

Best answer: So the QUESTION was "A ball is thrown HORIZONTALLY with a velocity of 26m/s. It travels a horizontal distance of 51 m before hitting the ground. ( statements of fact ). What is the height from which the ball is thrown? (the missing question). Neglect air resistance( statement of limiting conditions). ... show more
Best answer: So the QUESTION was "A ball is thrown HORIZONTALLY with a velocity of 26m/s. It travels a horizontal distance of 51 m before hitting the ground. ( statements of fact ). What is the height from which the ball is thrown? (the missing question). Neglect air resistance( statement of limiting conditions). Use g = 9.8 m/s^2 ( gravity varies so this sets the values for your location) "

Time of flight = d/v
= 51/26 s

Vertically the motion is h = 1/2 g t^2
= 1/2 * 9.8 * ( 51 / 26 )^2 = 18.9 m
4 answers · 5 days ago
• ### It seems the more advanced math and physics get the less important lectures are.?

5 answers · 5 days ago
• ### In physics, does -200 C have lower energy than 25 C, but -200 C is far more harmful than 25 C to human body?

Best answer: The amount of energy held in the material is NOT what causes the problem. It is the CHANGE in energy in the human that counts. Consider a vehicle moving at 100km/hr. It hits a stationary truck. The truck has no energy but the original vehicle loses ALL of its energy. Now compare it with the moving vehicle hitting... show more
Best answer: The amount of energy held in the material is NOT what causes the problem.
It is the CHANGE in energy in the human that counts.
Consider a vehicle moving at 100km/hr. It hits a stationary truck.
The truck has no energy but the original vehicle loses ALL of its energy.
Now compare it with the moving vehicle hitting a car moving in the same direction with some speed.
There is more total energy but the vehicle loses less in the collision. The CHANGE is smaller.
So if you take a human at 37 C interacting with something at 25 then compare it with the human interacting with something at -200
The second scenario makes a far bigger CHANGE to the human. So it also creates more harm accordingly.

There is no way to compare this with the energy in a photon of radio waves however.
The only thing that the photon can do, other than nothing, is to give its energy to something that it hits.
So the radio wave ALWAYS gives less energy in an interaction than the visible light does.

Now there are many other factors not addressed here. But following the principle that the lower the CHANGE in energy then the radio waves would be expected to be less hazardous to a human.
4 answers · 5 days ago
• ### What is 22 foot pounds in normal pounds "lb" of weight?

5 answers · 5 days ago
• ### Can water evaporate at room temperature?

I poured water into a cup and drew a line at where I first initially poured it. It’s been 3 days and the water has gone down about 2-3cm below the line. I have not exposed the water in the cup to sunlight, nor has anyone or anything touched the cup. It is isolated by itself and the water is going down. Any theories... show more
I poured water into a cup and drew a line at where I first initially poured it. It’s been 3 days and the water has gone down about 2-3cm below the line. I have not exposed the water in the cup to sunlight, nor has anyone or anything touched the cup. It is isolated by itself and the water is going down. Any theories as to why this may be? I thought water evaporated at 212°, not at room temperature. Thanks in advance!
15 answers · 1 week ago
• ### How would it change reality if e=mc3?

9 answers · 1 week ago
• ### How does the sun radiate the radio waves?

Best answer: The same way the Sun radiates ALL electromagnetic radiation because of nuclear fusion in the core. There are 2 nuclear fusion processes going on on the Sun's core.
Best answer: The same way the Sun radiates ALL electromagnetic radiation because of nuclear fusion in the core. There are 2 nuclear fusion processes going on on the Sun's core.
6 answers · 1 week ago
• ### A person exerts 130 joules of energy riding their bike up a hill. They gain 87 joules of gravitational potential energy. How to do?

3 answers · 6 days ago
• ### Why is the earth round ?

26 answers · 2 weeks ago
• ### Which one has higher energy? The cell phone’s radio waves or the bulb’s visible light?

Best answer: It's true that the energy in light radiations from the bulb (incandescent tungsten filament) is higher than the energy in radio waves from the cell phone. But, the method of physical interaction is different. When light falls on atoms in the body, it gets reflected based on the color pigments in the skin. There... show more
Best answer: It's true that the energy in light radiations from the bulb (incandescent tungsten filament) is higher than the energy in radio waves from the cell phone.
But, the method of physical interaction is different.
When light falls on atoms in the body, it gets reflected based on the color pigments in the skin. There is no harm done here.
When microwaves and high energy radio waves fall on the skin, there may be changes produced such as heating in the skin due to inter-molecular motion or there may be voltages produced. Radio waves are different from visible light EMR in this matter and so they cause harm while light waves do not cause harm.
5 answers · 7 days ago
• ### Where did the energy come from in order to work to be done?

[Purely Theoretical] While climbing up the stairs, the floor does not actually do work on you since your feet remain stationary while in contact with the floor. However, work is done by your legs on the rest of your body. Where did the energy come from in order to work to be done?
[Purely Theoretical] While climbing up the stairs, the floor does not actually do work on you since your feet remain stationary while in contact with the floor. However, work is done by your legs on the rest of your body. Where did the energy come from in order to work to be done?
9 answers · 2 weeks ago
• ### Can someone explain to me how to solve this problem! i know the answer is "in the downward direction" but i need it to be explained! Thanks!?

- A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. during this time, the acceleration of the ball is always...
- A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. during this time, the acceleration of the ball is always...
6 answers · 1 week ago
• ### Does time stop at the center of the Black Hole?

Best answer: Actually, it's thought that it stops *before* you'd reach the center - at the Event Horizon. If you could stand *on* the event horizon, time would tick away like normal, but if you looked out - you'd see the whole universe aging and dying in what - for you - only seems a few seconds... And, all the... show more
Best answer: Actually, it's thought that it stops *before* you'd reach the center - at the Event Horizon. If you could stand *on* the event horizon, time would tick away like normal, but if you looked out - you'd see the whole universe aging and dying in what - for you - only seems a few seconds...
And, all the light, energy, radiation, and in-falling debris is going to rain down on you seemingly all at once - frying you very quickly...
20 answers · 2 weeks ago
• ### What was it be like when the period electromagnetic force and weak nuclear force were united as one force in the early universe?

Best answer: Very hot beyond temperatures we speak of today with an expansion from a size smaller than a nano-particle to the size of our universe in a very small unit of time.
Best answer: Very hot beyond temperatures we speak of today with an expansion from a size smaller than a nano-particle to the size of our universe in a very small unit of time.
7 answers · 2 weeks ago
• ### Does force exist, or is it just a human invention?

10 answers · 2 weeks ago
• ### A question about Time Travel into the past specifically.?

Now Let me lay the scenario. Lets say we focus on me with all my knowledge as of right now. So Jack 1 of the present year of 2018 somehow travels back in time not in a physical state but a mental state with all the knowledge of Jack 1 and in the body of Jack 0 who is two years in the past. Lets say Jack 1 is 19 and... show more
Now Let me lay the scenario. Lets say we focus on me with all my knowledge as of right now. So Jack 1 of the present year of 2018 somehow travels back in time not in a physical state but a mental state with all the knowledge of Jack 1 and in the body of Jack 0 who is two years in the past. Lets say Jack 1 is 19 and Jack 0 is 17. Assume that Jack 0 has now traded places with Jack 1's body. As Jack 1 stuck 2 years in the past how would he go about getting back to his own time. Waiting perhaps and replicating the events of those two years as best as he could to recover the same outcome of what was his present life? If J1 were to get back to his own time how would he force it without having to wait and painstakingly walk on egg shells for two years. Would J2 be doing actions in J1's time? Would altering anything in the past as J1 in J2's body collapse the entire environment and stop the initial time travel? What would happen next? All scientifically as possible under the theories of gravitational and speed time travel. Im not a scientist just curious about different types of time travel so i may have some paradoxes and holes in some of the questions maybe all disregard those only what you can answer. If none of my stuff makes sense please explain plausible time travel in human experience not positrons. What would happen to a person where would it start where would it end who would be the future who would be the past and when would they meet.
5 answers · 1 week ago
• ### In a system where linear momentum is conserved; which of the following statements is correct?

1-No external forces can act on the system. 2-The sum of all the external forces on the system is zero. 3-The total momentum of the system is zero.
1-No external forces can act on the system. 2-The sum of all the external forces on the system is zero. 3-The total momentum of the system is zero.
5 answers · 1 week ago