If the accelerating voltage va were 250 volts, what would be the speed of the electrons emerging from the gun?


Answer 1



According to the law of conservation of energy, the amount of energy an electron gains after being accelerated is equal to its kinetic energy, that is, the electrical potential energy is converted into kinetic energy :

Solving for v and replacing the given voltage:

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Why was the idea of plate tectonics difficult for many scientists to accept for many years after it was first introduced? SCIENCE QUESTION


It's kind of funny really. The guy who invented the idea in the first place had actually been made fun of because the thought of that happening was improbable in their mind. Also, Wegener ( the guy who invented the idea) was not even a geologist but a meteorologist. But later it had been backed up due to earthquakes being record consecutively in one area, and the graphs turning out differently.

Use what you know about inertia to explain why you feel pressed back into the seat of a car when it accelerates


Because your inertia is going at a steady speed and it wanted to stay going that speed. When the car accelerates, your body isn't used to the new speed, so you get pressed back.

Jane is riding in a hot air balloon that is rising vertically at a constant speed of 3 m/s over a lake. She reaches out and drops a rock from the balloon when the distance from the rock to the water is 50 m. Use g = 10 m/s2, and let the up direction be positive. About how long after Jane drops the rock will it splash into the water?



The rock will splash into the water after Jane drops it.



  • Known data

and .

  • We are going to use the formula below

  • Letting up direction be positive and computing with the known data, we have

a second-grade polynomial, we obtain two roots, so and , due negative root has no sense, we take the positive one, so the rock will splash into the water after Jane drops it.


When falling through the air, which of the following objects will hit the ground first? a penny
a large poster
a shoe box
a cell phone



from a very very very high point, the object that is more streamlined and has more mass would touch the ground first (phone), because of drag, but from a normal height, for example, 6 feet, the difference would be so small that the penny, the box and the phone would touch the ground at the same time


This is a little more complicated that what it seems. In the vacuum, all objects would hit the ground at the same exact moment, because we would not have the effects of drag.

But the problem states that the objects are falling through the air, so there is drag involved. Drag is a friction force that acts against the force of gravity, and it increases according to the surface area of the object parallel to the floor, like parachutes for example.

In this case, the poster would act like a parachute and increase drag, thus falling last.

The second to last would be the shoe box, since its surface area would be bigger than either the phone or the penny.

To compare the penny and the phone we would need to look a the definition of terminal velocity, which is the speed of the falling object at the point where the drag and the gravitational force cancel themselves. At this point the more streamlined the object is, the higher its terminal velocity, yet the mass would play a part too, let's say the cellphone is is 100 times heavier than the penny, if the cellphone also experiences 100 times the drag force as the penny (at a given speed), then their terminal velocities will be the same, then they would touch the ground at the same time.

So the conclusion is this: if you drop them from a very very very high point, then the heaviest and more streamlined object would touch the ground first, meaning the phone, but if you drop them from, let's say, a table, they difference would be so small that it would not really matter and the phone, the penny and even the box, would hit the ground at the same time.

A cell phone! Hope this helps!

Write at least name of five devices which work under the principles of Physics. e.g: ultrasound machines .


Devices which work under the principles of physics include but are not limited to ultrasound machines, sonar transducers, computed tomography scan, magnetic resonance imaging, positron emission tomography, and neuroimaging.

The space shuttle travels at about 28,000 km per hour. Using that information, estimate how many hours it will take the shuttle to reach Saturn from Earth. Show your work. Convert your answer into scientific notation if necessary.


It depends what is the position of earth and saturn. Distance from earth to saturn varies depending on whether earth is between sun and saturn or sun is between earth and saturn. Obviously, the shortest distance will be if earth is between sun and saturn. we will take that the distance between earth and saturn is:

s = 1 275 000 000 km
The time required to travel that distance is:
t = s/v = 45535 hours or 1897.3 days

A snail can move approximately 0.30 meters per minute. How many meters can the snail cover in 15 minutes?


A snail can move approximately 0.30 meters per minute then it would cover 4.5 meters in 15 minutes.

What is speed?

The total distance covered by any object per unit of time is known as speed. It depends only on the magnitude of the moving object. The unit of speed is a meter/second. The generally considered unit for speed is a meter per second.

As given in the problem a snail can move approximately 0.30 meters per minute and we have to calculate the distance covered in 15 minutes.

speed of the snail  =  0.30 meters per minute

time = 15 minutes

distance covered by the snail = speed  ×time

distance covered by the snail = 0.30 ×15

distance covered by the snail = 4.5 meters

Thus, the distance covered by the snail in the 15 minutes would be 4.5 meters.

Learn more about speed from here,refer to the link ;


Distance = velocity (or speed) x time
so, distance = 0.30 meters.min x 15 mins
distance = 4.5 meters 

The green light from a traffic signal occurs at a wavelength of 522 nm. What is the frequency of this radiation?





We are given that

Wavelength of green light=522nm=


We have to find the frequency of this radiation.

We know that

Velocity of light=m/s

Where =Frequency of radiation

c=Velocity of light

=Wavelength of radiation

Using the formula


Hence, the frequency of radiation=Hz


Frequency of the radiation is


As per the question:



To calculate the frequency of the radiation, use the relation:



c = speed of light in vacuum =

f = frequency of the radiation

Use eqn (1):


A force of 20. Newtons to the left exerted on a cart for 10. Seconds. For what period of time must a 50.-newton force to the right act to produce an impulse of equal magnitude on the cart?


Impulse = (force) x (time)

The first impulse was (20 N) x (10 sec) = 200 meters/sec

The second one is (50 N) x (time) and we want it equal to the first one, so

(50 N) x (time) = 200 meters/sec

Divide each side by 50N :    Time = 200/50 = 4 seconds

By the way, the quantity we're playing with here is the cart's momentum.
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