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Naddika [18.5K]

2 years ago

13

A boy does 465 J of work pulling an empty wagon along level ground with a force of 111 N [31o below the horizontal]. A frictiona

l force of 155 N opposes the motion and is actually slowing the wagon down from an initial high velocity. The distance the wagon travels is

1 answer:

vovikov84 [41]2 years ago

6 0

Can you list the answer's

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A 20 watt lightbulb uses 20 Joules of energy every second.A person expends 50 watts of energy per stair when climbing up stairs.

Pachacha [2.7K]

20W = 20 J/s

Energy expended during climbing stairs = 50 W of energy/stair = 50J/stair

For 20 stairs, Total energy = 50x20 = 1000 J

This can light bulbs for, T= 1000J/20 J/s =50 seconds

6 0

2 years ago

Calculate the binding energy e of the boron nucleus 11 5b (1ev=1.602×10−19j). express your answer in millions of electron volts

nignag [31]

<span>Depends on the precision you're working to. proton mass ~ 1.00728 amu neutron mass ~ 1.00866 amu electron mass ~ electron mass = 0.000549 amu Binding mass is: mass of constituents - mass of atom Eg for nitrogen: (7*1.00728)-(7*1.00866)-(7*0.000549) -14.003074 = 0.11235amu Binding energy is: E=mc^2 where c is the speed of light. Nuclear physics is usually done in MeV[1] where 1 amu is about 931.5MeV/c^2. So: 0.11235 * 931.5 = 104.6MeV Binding energy per nucleon is total energy divided by number of nucleons. 104.6/14 = 7.47MeV This is probably about right; it sounds like the right size! Do the same thing for D/E/F and recheck using your numbers & you shouldn't go far wrong :) 1 - have you done this? MeV is Mega electron Volts, where one electronVolt (or eV) is the change in potential energy by moving one electron up a 1 volt potential. ie energy = charge * potential, so 1eV is about 1.6x10^-19J (the same number as the charge of an electron but in Joules). It's a measure of energy, but by E=mc^2 you can swap between energy and mass using the c^2 factor. Most nuclear physicists report mass in units of MeV/c^2 - so you know that its rest mass energy is that number in MeV.</span>

7 0

2 years ago

A woman with mass 50 kg is standing on the rim of a large horizontal disk that is rotating at 0.80 rev/s about an axis through i

irinina [24]

Answer:

Angular momentum of disc + woman is given as

$L = 9759 kg m^2/s$

Explanation:

As we know that the angular momentum of disc + woman is given as

$L = (I_{disk} + I_{woman}) \omega$

here we know for disk moment of inertia is given as

$I_{disk} = \frac{1}{2}mR^2$

$I_{disk} = \frac{1}{2}(110)(4.3)^2 = 1017 kg m^2$

similarly for woman we will have

$I_{woman} = MR^2$

$I_{woman} = (50)(4.3^2)$

$I_{woman} = 924.5 kg m^2$

so we will have

$\omega = 2\pi (0.80) rad/s$

so angular momentum is given as

$L = (1017 + 924.5)(2\pi 0.80)$

$L = 9759 kg m^2/s$

7 0

2 years ago

A soccer player runs up behind a 0.450-kg soccer ball traveling at 3.20 m/s and kicks it in the same direction as it is moving,

NISA [10]

To develop this problem it is necessary to use the concepts related to Impulse.

The impulse is defined as the change in velocity at the rate of mass, that is

$L = m\Delta V,$

Where,

m = Mass

$\Delta V =$ Change in Velocity

This change in velocity can be expressed as,

$L = m(v_2-v_1)$

$L = 0.45*(12.8 - 3.2)$

$L = 0.45*9.6$

$L= 4.32 Kg.m/s$

Therefore the magnitude of the impulse is 4.32 Kg.m/s

7 0

2 years ago

A small house was built on an island off a perfectly straight shoreline. The point B on the shoreline that is closest to the isl

abruzzese [7]

Answer:

Q should be 4.8 miles east of B.

Explanation:

As the diagram shows, we can simply express the construction cost as a function of angle θ (represented in the diagram).

The length of the pipe in water (represented with blue) = 6/cos θ

The length of the pipe on land (represented with brown) = (8-6*tan θ)

Construction Cost = (6/cos θ) (6000) + (8-6*tan θ)(3750)

The above function represents the construction cost and is in terms of θ

The value of θ varies from 0 degrees to 53.13 degrees as per the diagram.

We can take the derivative of Construction Cost function with respect to θ and equate it to zero to find the angle θ at which the construction cost is minimum.

d(Construction Cost)/d θ = -4500(5*sec θ – 8*tan θ)(sec θ)

-4500(5*sec θ – 8*tan θ) (sec θ) = 0

θ = 38.68 degrees

Using the value of θ, we can find the distance of Q from B.

Distance of Q from B = 6*tan θ

Distance of Q from B = 6*tan (38.68 degrees)

Distance of Q from B = 4.8 miles

7 0

2 years ago