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sweet [91]
3 years ago
13

You've always wondered about the acceleration of the elevators in the 101 story-tall Empire State Building. One day, while visit

ing New York, you take your bathroom scale into the elevator and stand on them. The scales read 160 lb as the door closes. The reading varies between 130 lb and 180 lb as the elevator travels 101 floors.
a. What is the magnitude of the acceleration as the elevator starts upward?
b. What is the magnitude of the acceleration as the elevator brakes to a stop?
Physics
1 answer:
Arte-miy333 [17]3 years ago
8 0

Answer:

a)  a = 4 ft / s² , b) a = -6 ft / s²

Explanation:

The balance is subjected to two forces: the weight of the person directed downward and the spring reaction directed upward.

When the person rides the elevator, the acceleration is zero

            F - W = 0

            F = W

            F = 160 lb

let's find the mass of the body

            W = mg

            m = W / g

            m = 160/32

           m = 5 slug

A) when the elevator is moving up

            F - W = m a

            F = W + m a

            F - W / m = m a

            F = m (g + a)

therefore the scale reading (F) must be higher, in this case F = 180 lb

             a = F / m - g

            a = 180 - 160)/5

            a = 4 ft / s²

b) when the elevator is stopping

in this case the direction is opposite to the speed, that is to say downwards

              F- W = m (-a)

              a = W - F / m

              a = 130 -160 /5

              a = -6 ft / s²

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storchak [24]

Answer: machine's efficiency = 82.2%

Explanation:

Efficiency of a machine is the capability of a machine to convert input to output without waste.

It can be expressed as

Efficiency = output/ input × 100%

Output = 7,023N

Imput = 8,542N

Efficiency = 7,023N/8,542N × 100%

Efficiency = 82.2%

4 0
3 years ago
A reconnaissance plane flies 545 km away from
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Answer:

681.6/ms

Explanation:

A reconnaissance plane flies 545 km away from  its base at 568 m/s. then flies back to its base  at 852 m/s.

What is its average speed?

Answer in its of m/s

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6 0
3 years ago
2..Read the following statements carefully and choose the correct option
Softa [21]

Answer:

statement 1 is correct

2 not sure

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2 years ago
A bullet with a mass 2.25g is fired up into the air with a velocity of 187.5 m/s. What is the maximum height of the bullet
Ksivusya [100]

Answer:

1793.7m

Explanation:

From the principle of conservation of energy; the kinetic energy substended by the object equals the potential energy sustain by the object when it gets to its maximum position.

Now the kinetic energy; is

K.E = 1/2 × m × v2

Where m is mass

v is velocity

Hence.

K.E = 1/2 × 2.25 × (187.5)^2

Now this should be same with the potential energy which is given as;

P.E = m× g× h

Where m is mass of object

g is acceleration of free fall due to gravity = 9.8m/S2

h is maximum height substain by the object.

Hence P.E = 2.25 × 9.8 × h

From the foregoing analysis of energy conversation it implies;

1/2 × 2.25 × (187.5)^2 =2.25 × 9.8 × h

=> 1/2 × (187.5)^2 = 9.8 × h

=>1/2 × (187.5)^2 / 9.8 = h

=> 1793.69m = h

h= 1793.69m

h =1793.7m to 1 decimal place

3 0
3 years ago
If a 15 kg mass accelerates at a rate of 4 m/s2, what net force acts on it?
jarptica [38.1K]
<h2>Answer: D 60N</h2>

<h3>Explanation:</h3>

Mass(M)=15 kg

Acceleration(A)=4 m/s2

Force=?

Now,

Force(F)=M×A

F=15×4

F=60N Ans

5 0
3 years ago
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