your friends says the helium in your birthday helium comes from radioactive decays. What is your response?

How can a calculated height be greater than an actual height?

sammy [17]

Answer:

mesuring heigh and weight is important

3 0

3 years ago

What is the closeness of measured value to an accepted value?

kotykmax [81]

Accuracy?

filler text filler text filler text

3 0

3 years ago

If an object is not moving are the forces acting on it balanced? Yes or no?why?

xxMikexx [17]

This is another time to look at Newton's 2nd law of motion:

Net Force = (mass) x (acceleration)

If the object is not moving, then its acceleration is certainly zero, and Newton's law looks like this:

Net Force = (mass) x (zero)

or Net Force = (zero) .

"Net Force = zero" means that if there ARE any forces acting on the object, then they add up to zero, and we call them "balanced" forces.

So the answer is '<em>yes</em>', and that's why.

6 0

3 years ago

Two bowling balls each have a mass of 6.8 kg. They are located next to each other with their centers 21.8 cm apart. What gravita

12345 [234]

Answer:

6.49 x 10^-8 N

Explanation:

formula is

F= G * ((m1 * m2)/r^2)

F = 6.67x10^-11 * ((6.8*6.8/.218)

F = 6.49 x 10^-8 Newtons

3 0

3 years ago

Lasers are now used in eye surgery. Given the wavelength of a certain laser is 514 nm and the power of the laser is 1.1 W, how m

Leno4ka [110]

Answer: $1.593*10^{17} photons$ released if the laser is used 0.056 s during the surgery

Explanation:

First, you have to calculate the energy of each photon according to Einstein's theoty, given by:

$E =\frac{hc}{\lambda}$

Where $\lambda$ is the wavelength, $h$ is the Planck's constant and $h$ is the speed of light

$h = 6.626*10^{-34} \frac{m^{2} kg }{s}$ -> Planck's constant

$c = 3*10^{8} \frac{m}{s}$ -> Speed of light

So, replacing in the equation:

$E =\frac{ 6.626*10^{-34} \frac{m^{2} kg }{s}*3*10^{8} \frac{m}{s}}{514*10^-9 m}$

Then, the energy of each released photon by the laser is:

$E = 3.867*10^{-19} \frac{J}{photons}$

After, you do the inverse of the energy per phothon and as a result, you will have the number of photons in a Joule of energy:

$\frac{1}{3.867*10^{-19}} = 2.586*10^{18} \frac{photons}{J}$

The power of the laser is 1.1 W, or 1.1 J/s, that means that you can calculate how many photons the laser realease every second:

$2.586*10^{18}\frac{photons}{J} * 1.1 \frac{J}{s} = 2.844*10^{18} \frac{photons}{s}$

And by doing a simple rule of three, if $2.844*10^{18} photons$ are released every second, then in 0.056 s:

$0.056 s*2.844*10^{18} \frac{photons}{s} = 1.593*10^{17} photons$ are released during the surgery

5 0

3 years ago