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4 years ago

11

A mover hoists a 200 kg piano from the ground to a height of 10 m using a single pulley. What was the change in the pianos energ

y? a. 20j b. 200j c. 2000j d. 20000

2 answers:

RideAnS [48]4 years ago

7 0

P.E= Mass x gravity x height (standard gravity = 10m/s approaximately)
= 200x10x10= 20000j (D)

aivan3 [116]4 years ago

3 0

Answer: d. 20000 J

Explanation:

Potential energy is the energy possessed by an object by virtue of its position.

$P.E=m\times g\times h$

m= mass of object = 200 kg

g = acceleration due to gravity = $10ms^{-2}$

h = height of an object

1. when h= 10 m

$P.E=200\times 10ms^{-2}\times 10m=20000Joules$

2. when h= 0 m

$P.E=200\times 10ms^{-2}\times 0m=0Joules$

Thus change in energy=(20000-0)Joules=20000Joules.

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If a trapezoidal channel has side slopes of 1:1, hydraulic depth is 5 feet, the bottom width is 8 feet, flow is 2,312 cubic feet

Evgesh-ka [11]

Answer:

$S = \dfrac{1}{2.5}$

Explanation:

given,

side slope = 1 : 1

hydraulic depth(y) = 5 ft

bottom width (b)= 8 ft

x = 1

Q = 2,312 ft³/s

n = 0.013

slope of channel = ?

$R = \dfrac{A}{P}$

$R = \dfrac{y(b + xy)}{b+2y\sqrt{1+x^2}}$

$R = \dfrac{5(8+ 5)}{8+2\times 5\sqrt{1+1^2}}$

R = 4.69 m

using manning's equation

$Q = \dfrac{1}{n}AR^{2/3} S^{1/2}$

$2312= \dfrac{1}{0.013}\times (5(8+5))\times 4.69^{2/3} S^{1/2}$

$2312=14009.37\times S^{1/2}$

S = 0.406

$S = \dfrac{1}{2.5}$

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3 years ago

6. A pitcher throws a ball toward home plate 18.39 meters away. If the ball is traveling at a constant 40.0 m/s, how long does i

Kruka [31]

18.39 I don’t know this

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3 years ago

A car is moving at 19 m/s along a curve on a horizontal plane with radius of curvature 49m.

JulsSmile [24]

Answer:

$\mu =0.75$

Explanation:

<u>Frictional Force </u>

When the car is moving along the curve, it receives a force that tries to take it from the road. It's called centripetal force and the formula to compute it is:

$F_c=m.a_c$

The centripetal acceleration a_c is computed as

$\displaystyle a_c=\frac{v^2}{r}$

Where v is the tangent speed of the car and r is the radius of curvature. Replacing the formula into the first one

$F_c=m.\frac{v^2}{r}$

For the car to keep on the track, the friction must have the exact same value of the centripetal force and balance the forces. The friction force is computed as

$F_r=\mu N$

The normal force N is equal to the weight of the car, thus

$F_r=\mu .m.g$

Equating both forces

$\displaystyle \mu .m.g=m.\frac{v^2}{r}$

Simplifying

$\displaystyle \mu =\frac{v^2}{rg}$

Substituting the values

$\displaystyle \mu =\frac{19^2}{(49)(9.8)}$

$\boxed{\mu =0.75}$

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4 years ago

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Read 2 more answers

Identify the pros and cons of using mirrors versus lenses in each of the following applications:

disa [49]

Answer:

Explanation:

A lens – An object, usually made of glass, that focuses or defocuses the light that passes through it.

A mirror – A smooth surface, usually made of glass with reflective material painted on the underside, that reflects light so as to give an image of what is in front of it.

Telescope – monocular optical instrument possessing magnification for observing distant objects, especially in astronomy.

Refracting telescopes – are telescopes that use lenses are and those that use concave parabolic mirrors are called reflecting telescopes.

Pros of mirror telescope

• They are easier to construct and not expensive to produce

• made larger and more durable (more light can be directed to the eyepiece which is good)

• cannot have any occlusions

• mirrors have less spherical aberration

• reflect all wavelengths of light equally

• more magnification power for cheaper version

Cons of mirror prisms

• it must also be realigned after cleaning, which can be expensive - maintenance disadvantage

• Reflective Surface Disadvantage

Pros of Lenses telescope

• Easy to use

• More reliable

Cons of Lens telescope

• are not easy to construct and expensive to produce

• May have occlusions

• spherical aberration are more

• Doesnt reflect wavelengths of light equally they bend light differently

• Less magnification power for cheaper version

• heavy

• Longer body

Pro of Mirror periscope

• it helps us to see further than our view that is what is above us or sometimes even below us.

•Light weight

disadvantage:

• it may not work properly and show distorted images due to fog. ; Some have a narrow field of view ; May be detected by others Ungainly (long, takes up space),

•Not as rugged as prisms.

• Maintenance of reflection surface

Pros of Prism periscopes

• incorporated lenses for magnification and function as telescopes.

• They typically employ prisms and total internal reflection instead of mirrors, because prisms, which do not require coatings on the reflecting surface, are much more rugged than mirrors.

• May be fitted with additional optical capabilities such as range-finding and targeting.

Cons.

•mechanically disadvantage: Complex optically ; Some have a narrow field of view ; May be detected by others

Ungainly (long, takes up space)

• Heavy weight

Lens - Terrestrial telescope

Pro: An advantage is that it makes it possible to vary the magnification of the telescope.

Cons- This system has the disadvantage increasing the length of the telescope.

Mirror- Terrestrial telescope (Cassegrain)

Pro: Good for distant terrestrial viewing.

greater magnification is attained.

They are more shorter

Cons- It is not what people expect a telescope to look like.

Slight light loss due to secondary mirror obstruction compared to refractors. Generally not suited for most terrestrial applications nor for to view objects in the sky.

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3 years ago