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Vladimir79 [104]
3 years ago
13

A weight lifter lifts a 345 N set of weights from ground level to a position over his head, a vertical distance of 1.89 m. How m

uch work does the weight lifter do, assuming he moves the weights at constant speed?
Physics
1 answer:
Pavlova-9 [17]3 years ago
3 0

Answer:652.05 J

Explanation:

Given

Weight of lifter W=345 N

vertical distance move h=1.89 m

Work done in lifting the weight is equal change in Potential Energy of weight

Change in Potential Energy =m g h

\Delta PE=345 \times 1.89=652.05 J

therefore work done is equal to 652.05 J  

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A charged paint is spread in a very thin uniform layer over the surface of a plastic sphere of diameter 13.0 cm , giving it a ch
Leokris [45]

a) Electric field inside the paint layer: zero

b) Electric field just outside the paint layer: -3.62\cdot 10^7 N/C

c) Electric field 8.00 cm outside the paint layer: -7.27\cdot 10^7 N/C

Explanation:

a)

We can find the electric field inside the paint layer by applying Gauss Law: the total flux of the electric field through a gaussian surface is equal to the charge contained within the surface divided by the vacuum permittivity, mathematically:

\int EdS = \frac{q}{\epsilon_0}

where

E is the electric field

dS is the element of surface

q is the charge within the gaussian surface

\epsilon_0 = 8.85\cdot 10^{-12}F/m is the vacuum permittivity

Here we want to find the electric field just inside the paint layer, so we take a sphere of radius r as Gaussian surface, where

R = 6.5 cm = 0.065 m is the radius of the plastic sphere (half the diameter)

By taking the sphere of radius r, we note that the net charge inside this sphere is zero, therefore

q=0

So we have

\int E dS=0

which means that the electric field inside the paint layer is zero.

b)

Now we want to find the electric field just outside the paint layer: therefore, we take a Gaussian sphere of radius

r=R=0.065 m

The area of the surface is

A=4\pi R^2

And since the electric field is perpendicular to the surface at any point, Gauss Law becomes

E\cdot 4\pi R^2 = \frac{q}{\epsilon_0}

The charge included within the sphere in this case is the charge on the paint layer, therefore

q=-17.0\mu C=-17.0\cdot 10^{-6}C

So, the electric field is:

E=\frac{q}{4\pi \epsilon_0 R^2}=\frac{-17.0\cdot 10^{-6}}{4\pi(8.85\cdot 10^{-12})(0.065)^2}=-3.62\cdot 10^7 N/C

where the negative sign means the direction of the field is inward, since the charge is negative.

c)

Here we want to calculate the electric field 8.00 cm outside the surface of the paint layer.

Therefore, we have to take a Gaussian sphere of radius:

r=8.00 cm + R = 8.00 + 6.50 = 14.5 cm = 0.145 m

Gauss theorem this time becomes

E\cdot 4\pi r^2 = \frac{q}{\epsilon_0}

And the charge included within the sphere is again the charge on the paint layer,

q=-17.0\mu C=-17.0\cdot 10^{-6}C

Therefore, the electric field is

E=\frac{q}{4\pi \epsilon_0 r^2}=\frac{-17.0\cdot 10^{-6}}{4\pi(8.85\cdot 10^{-12})(0.145)^2}=-7.27\cdot 10^7 N/C

Learn more about electric field:

brainly.com/question/8960054

brainly.com/question/4273177

#LearnwithBrainly

5 0
3 years ago
A water line with an internal radius of 5.29 x 10-3 m is connected to a shower head that has 15 holes. The speed of the water in
fiasKO [112]

Answer:

(a) 3.44 x 10^-3 m^3/s

(b) 8.4 m/s

Explanation:

area of water line, A = 5.29 x 10^-3 m

number of holes, N = 15

Speed of water in line, V = 0.651 m/s

(a) Volume flow rate is given by

V = area of water line x speed of water in water line

V = 5.29 x 10^-3 x 0.651 = 3.44 x 10^-3 m^3/s

(b) area of one hole, a = 4.13 x 10^-4 m

Let v be the velocity of water in each hole

According to the equation of continuity

A x V = a x v

5.29 x 10^-3 x 0.651 = 4.1 x 10^-4 x v

v = 8.4 m/s  

5 0
3 years ago
Pls help I really need help w this one Tnks
lyudmila [28]
Sorry I do not know srry
6 0
2 years ago
Referring to the diagram above, predict what will happen when the switch is closed. Explain your answer.
alisha [4.7K]

Answer

The nail will become an electromagnet.

Explanation

When the switched is closed , a current will flow in the insulated wire. Then the current flows through the coil around the iron nail, it will induce am magnetic filed inside the nail.  The nail becomes a magnet because it is made of magnetic material.  As long as there is current flowing through the current, there nail will remain a magnet.


7 0
3 years ago
Imagine a 15kg block moving with a speed of 20m/s. Calculate the kinetic energy of this block. (Show the equation, show your wor
dmitriy555 [2]

Answer:

The answer to your question is:        Ke = 3000 Joules

Explanation:

Data

mass = 15 kg

speed = 20 m/s

Kinetic energy = ?

Equation

               Ke = \frac{1}{2}mv^{2}

               Ke = \frac{1}{2}(15)(20)^{2}

                Ke = 3000 Joules

5 0
3 years ago
Read 2 more answers
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