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3 years ago

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A construction worker uses 1,000 J of work to screw two boards together. The screw does 855 J of work. Calculate the efficiency

of the screw.
PLZ HELP!!!

1 answer:

Dovator [93]3 years ago

7 0

Answer:

The efficiency of the screw is 85.5%

Explanation:

to calculate efficiency you have to do

efficiency=energy output/ energy input × 100%

so e=855/1000 × 100%=85.5%

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When placed 1.18 m apart, the force each exerts on the other is 11.2 N and is repulsive. What is the charge on each

aleksandr82 [10.1K]

Answer:

$q=41.62\ \mu C$

Explanation:

Given that,

Force between two objects, F = 11.2 N

Distance between objects, d = 1.18 m

We need to find the charge on each objects. The force between charges is as follows :

$F=\dfrac{kq^2}{r^2}\\\\q=\sqrt{\dfrac{Fr^2}{k}} \\\\q=\sqrt{\dfrac{11.2\times (1.18)^2}{9\times 10^9}} \\\\q=41.62\ \mu C$

So, the charge on each sphere is $41.62\ \mu C$ .

7 0

3 years ago

Question 3 A woman sitting in a stationary car notices a man cycling past her at 40 km/hr. Five seconds after he passes her car,

Naya [18.7K]

The shortest possible distance in which she catches up with the man is 129.7 m.

The given parameters:

speed of the man, v₁ = 40 km/hr

speed of the woman, v₂ = 70 km/hr

time when the woman started moving, t₁ = 5 seconds

To find:

the shortest distance when she catches up with the man

Convert the given speed in km/h to m/s

3.6 km/h = 1 m/s
40 km/h = 40/3.6 = 11.11 m/s
70 km/h = 70/3.6 = 19.44 m/s

Calculate the distance moved by the man before she started following him.

Distance moved by the man = speed x time

= 11.11 m/s x 5 s

= 55.55 m

Let the time the woman catches up with the man = t

Apply the following simple principle to calculate the time.

The man is moving forward and the woman is moving forward to close the gap between them, thus both speeds are working against each other.

$(v_2-v_1)t = 55.55 \ m$

the difference in the speed is because they are working against each other.

$(19.44 - 11.11)t = 55.55\\\\8.33t = 55.55\\\\t = \frac{55.55}{8.33} \\\\t = 6.67 \ s$

The time when the woman catches up with the man = 6.67 s

The shortest distance at which the woman catches up with the man is calculated as;

Shortest distance = woman's speed x time when she catches up

= 19.44 m/s x 6.67 s

= 129.7 m

Thus, the shortest possible distance in which she catches up with the man is 129.7 m.

Learn more here: https://brainly.in/question/9541933?tbs_match=3

5 0

3 years ago

What is the elastic potential energy of a spring that is compressed a distance of 0.35 m and has a spring constant of 71.8 N/m?

Vitek1552 [10]

Answer:

P.E = 4.398 Joules.

Explanation:

Given the following data;

Spring constant, k = 71.8N/m

Displacement, x = 0.35m

To find the elastic potential energy;

The elastic potential energy of an object is given by the formula;

$P.E = \frac {1}{2}kx^{2}$

Substituting into the equation, we have;

$P.E = \frac {1}{2}*71.8 *(0.35)^{2}$

$P.E = 35.9 * 0.1225$

Elastic potential energy = 4.398 Joules.

<em>Therefore, the elastic potential energy of the spring is 4.398 Joules. </em>

3 0

3 years ago

The half life of carbon-14 is 5730 years. How old is a bone if it presently contains 0.3125 g of carbon-14, but it was estimated

TiliK225 [7]

The age of the bone is 45840 years.

We'll begin by calculating the number of half-lives that has elapsed.

Amount remaining (N) = 0.3125 g

Initial amount (N₀) = 80 g

<h3>Number of half-lives (n) =? </h3>

N × 2ⁿ = N₀

0.3125 × 2ⁿ = 80

Divide both side by 0.3125

2ⁿ = 80 / 0.3125

2ⁿ = 256

2ⁿ = 2⁸

<h3>n = 8</h3>

Thus, 8 half-lives has elapsed

Finally, we shall determine the age of the bone.

Half-life (t½) = 5730 years

Number of half-lives (n) = 8

<h3>Time (t) =? </h3>

t = n × t½

t = 8 × 5730

<h3>t = 45840 years </h3>

Therefore, the age of the bone is 45840 years.

Learn more on half-life: brainly.com/question/15900105

5 0

3 years ago

A plane wall with constant properties is initially at a uniform temperature To. Suddenly, the surface at x = L is exposed to a c

Rzqust [24]

Answer:

The distribution is as depicted in the attached figure.

Explanation:

From the given data

The plane wall is initially with constant properties is initially at a uniform temperature, To.
Suddenly the surface x=L is exposed to convection process such that T∞>To.
The other surface x=0 is maintained at To

Uniform volumetric heating q' such that the steady state temperature exceeds T∞.

Assumptions which are valid are

There is only conduction in 1-D.
The system bears constant properties.
The volumetric heat generation is uniform

From the given data, the condition are as follows

<u>Initial Condition</u>

At t≤0

$T(x,0)=T_o$

This indicates that initially the temperature distribution was independent of x and is indicated as a straight line.

<u>Boundary Conditions</u>

<u>At x=0</u>

<u /> $T(0,t)=T_o$ <u />

This indicates that the temperature on the x=0 plane will be equal to To which will rise further due to the volumetric heat generation.

<u>At x=L</u>

<u /> $-k\frac{\partial T}{\partial x}]_{x=L}=h[T(L,t)-T_{\infty}]$ <u />

This indicates that at the time t, the rate of conduction and the rate of convection will be equal at x=L.

The temperature distribution along with the schematics are given in the attached figure.

Further the heat flux is inferred from the temperature distribution using the Fourier law and is also as in the attached figure.

It is important to note that as T(x,∞)>T∞ and T∞>To thus the heat on both the boundaries will flow away from the wall.

3 0

3 years ago