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3 years ago

Methods to reduce the frictional force between the an object and surface which it is in contact.

Physics

1 answer:

telo118 [61]3 years ago

7 0

Use of lubricant
Use of ball bearers
Use of streamlined body
Use of graphite

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The following table lists the work functions of a few commonmetals, measured in electron volts.

steposvetlana [31]

Answer:

Lithium

Explanation:

The equation for the photoelectric effect is

$\frac{hc}{\lambda}= \phi + K_{max}$

where

$\frac{hc}{\lambda}$ is the energy of the incident photon, with

h being the Planck constant

c is the speed of light

$\lambda$ is the wavelength of the photon

$\phi$ is the work function of the metal (the minimum energy needed to extract the photoelectron from the metal)

$K_{max}$ is the maximum kinetic energy of the emitted photoelectrons

In this problem, we have

$\lambda= 190 nm = 1.9\cdot 10^{-7}m$ is the wavelength of the incident photon

$K_{max}=4.0 eV$ is the maximum kinetic energy of the electrons

First of all we can find the energy of the incident photon

$E=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{1.90\cdot 10^{-7} m}=1.05\cdot 10^{-18} J$

Converting into electronvolts,

$E=\frac{1.05\cdot 10^{-18} J}{1.6\cdot 10^{-19} J/eV}=6.6 eV$

So now we can re-arrange the equation of the photoelectric effect to find the work function of the metal

$\phi = E-K_{max}=6.6 eV - 4.0 eV=2.6 eV$

So the metal is most likely Lithium, which has a work function of 2.5 eV.

3 0

3 years ago

A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 250-kg crate. If g-9.

seraphim [82]

Answer:

0.31

Explanation:

horizontal force, F = 750 N

mass of crate, m = 250 kg

g = 9.8 m/s^2

The friction force becomes applied force = 750 N

According to the laws of friction,

Friction force = μ x Normal reaction of the surface

here, μ be the coefficient of friction

750 = μ x m g

750 = μ x 250 x 9.8

μ = 0.31

Thus, the coefficient of static friction is 0.31.

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3 years ago

Why are viruses hard to fight

ki77a [65]

Answer:Compared to other pathogens, such as bacteria, viruses are minuscule. And because they have none of the hallmarks of living things — a metabolism or the ability to reproduce on their own, for example — they are harder to target with drugs.

Explanation:

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3 years ago

A metal pot feels hot to the touch, but the plastic handle does not. Which type of material is the plastic handle? A. A thermal

gtnhenbr [62]

D is the answer..........

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Why does a small particle size generally cause a reaction to proceed faster?

Ugo [173]

I think its a. i am not sure though.

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