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madreJ [45]
3 years ago
14

The suspension cable of a 1,000 kg elevator snaps, sending the elevator moving downward through its shaft. The emergency brakes

of the elevator stop the elevator shortly before it reaches the bottom of the shaft. If the elevator fell a distance of 100 m starting from rest, the heat that the brakes must dissipate to bring the elevator safely to rest is (A) 100 J (B) 1,000 J (C) 10,000 J (D) 100,000 J (E) 1,000,000 J
Physics
1 answer:
tester [92]3 years ago
4 0

Answer:

option (E) 1,000,000 J

Explanation:

Given:

Mass of the suspension cable, m = 1,000 kg

Distance, h = 100 m

Now,

from the work energy theorem

Work done by the gravity = Work done by brake

or

mgh = Work done by brake

where, g is the acceleration due to the gravity = 10 m/s²

or

Work done by brake  = 1000 × 10 × 100

or

Work done by brake = 1,000,000 J

this work done is the release of heat in the brakes

Hence, the correct answer is option (E) 1,000,000 J

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A police car moving at 36.0 m/s is chasing a speeding motorist traveling at 30.0 m/s. The police car has a siren that emits soun
maxonik [38]

Answer:

The frequency heard by the motorist is 4313.2 Hz.

Explanation:

let f1 be the frequency emited by the police car and f2 be the frequency heard by the motorist, let v1 be the speed of the police car and v2 be the speed of the motorist and v = 343 m/s be the speed of sound.

because the police car is moving towards the motorist at a higher speed, then the motorist will hear a increasing frequency and according to Dopper effect, that frequency is given by:

f1 =  [(v + v2/(v - v1))]×(f2)

   = [( 343 + 30)/(343 - 36)]×(3550)

   = 4313.2 Hz

Therefore, the frequency heard by the motorist is 4313.2 Hz.

5 0
2 years ago
Car A is traveling west at 40 mi/h and car B is traveling north at 40 mi/h. Both are headed for the intersection of the two road
Gwar [14]

Explanation:

It is given that,

    \frac{dx}{dt} = -40 mi/h,     \frac{dx}{dt} = -40 mi/h

The negative sign indicates that x and y are decreasing.

We have to find \frac{dz}{dt}. Equation for the given variables according to the Pythagoras theorem is as follows.

              z^{2} = x^{2} + y^{2}

Now, we will differentiate each side w.r.t 't' as follows.

        2z\frac{dz}{dt} = 2x\frac{dx}{dt} + 2y\frac{dy}{dt}

or,          \frac{dz}{dt} = \frac{1}{z}(x\frac{dx}{dt} + y\frac{dy}{dt})

So, when x = 4 mi, and y = 3 mi then z = 5 mi.

As,       \frac{dz}{dt} = \frac{1}{z}(x\frac{dx}{dt} + y\frac{dy}{dt})

                       = \frac{1}{5}(4 \times (-40) + 3 \times (-40))

                       = \frac{-140 - 120}{5}

                       = 52

Thus, we can conclude that the cars are approaching at a rate of 52 mi/h.

7 0
3 years ago
A track coach records how long it takes a sprinter to run 100 meters the track coach is recording what dimension of behavior
melamori03 [73]
Behavior has at least six dimensions, which are: frequency, duration, latency, topography, locus, and force. Since the coach is recording how long it takes, the track coach is recording the duration behavior because duration is a synonym for time. Duration is your answer.
5 0
3 years ago
The average intensity of sunlight at the top of the earth's atmosphere in 1390 w/m2. what is the maximum energy that a 34-m x 46
slavikrds [6]
Panel surface area =34m×46m=1,564m^2
total power =1564m^2×1390w/m^2
=2173960watts
now you must calculate total energy.
Energy = power×Time
However time must be in seconds so we multiply 2hrs×60min×60s=7200seconds
7200s×2173960w =15,652,512,000 joules of energy
7 0
3 years ago
If I push on the wall with 75 Newtons of force, the wall will push back with __
Scilla [17]

Answer: 0

Explanation:

75 newtons will push back canceling it out make it 0

7 0
3 years ago
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