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olchik [2.2K]
3 years ago
12

An elevator held by a single cable is ascending but slowing down. Is the work done by tension positive, negative, or zero? What

about the work done by gravity? Explain
Physics
1 answer:
inessss [21]3 years ago
8 0

Explanation:

1.) Work = Force*Distance

2.) The direction of motion lies in the same direction as the tension in the cable. So the work done by tension would be positive.

3.) The direction of the weight (due to gravity) would act opposite to the direction of motion of the elevator, so work done by gravity becomes negative.

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I would like to know why this is the correct answer
Marta_Voda [28]

Answer:

see below

Explanation:

First, the obvious, as you press the gas pedal harder the acceleration goes up as well.  Conversely, is you do not press the pedal, you will not accelerate.  This determines that is I press the gas pedal, it will CAUSE the car to accelerate.  This proves causation.

Now, correlation.  The definition of correlation in statistics is any statistical relationship between two random variables or data.  This simply means that these two events are connected to one another.  A POSITIVE correlation is when two correlated events move in the same direction as one another.  I have added a graph to help visualize this.  In this problem as the gas is pressed harder, the acceleration increases.  If the pressure on the pedal was decreased, then the acceleration also decreases.  If the pressure on the pedal is constant, the the acceleration is constant.

I hope this helps!

4 0
3 years ago
A 1kw electric heater is switched on for ten minutes. how much heat does it produce​
Ainat [17]

H= P × t

1kW= 1000w

10 min = 600s

H= 1000×600=600,000J

=> 143.40kcal

4 0
3 years ago
You hang a heavy ball with a mass of 30 kg from a tungsten rod 2.8 m long by 1.5 mm by 2.6 mm. You measure the stretch of the ro
guajiro [1.7K]

Answer:

Young's modulus (Y) = 3.56×10^11 N/m^2

The speed of sound in tungsten = 6166.4 m/s

Explanation:

Young's modulus (Y) = stress/strain

Stress = force/area

Force = mg = 30×9.8 = 294 N

Area = 1.5 × 2.6 = 3.9 mm^2 = 3.9/10^6 = 3.9×10^-6 m^2

Stress = 294/3.9×10^-6 = 7.54×10^7 N/m^2

Strain = extension/length

Extension = 0.000594 m

Length = 2.8 m

Strain = 0.000594/2.8 = 2.12×10^-4

Y = 7.54×10^7/2.12×10^-4 = 3.56×10^11 N/m^2

Y = h × rho × g

rho = 18.7 g/cm^3 = 18.7 g/cm^3 × 1 kg/1000 g × (100 cm/1 m)^3 = 18,700 kg/m^3

h = 3.56×10^11/(18,700×9.8) = 1.94×10^6 m

From the equations of motion

v^2 = u^2 + 2gh =

Initial speed (u) = 0 m/s

v = sqrt (2×9.8×1.94×10^6)

v = 6166.4 m/s

7 0
3 years ago
Read 2 more answers
A bolt is dropped from a bridge under construction, falling 94 m to the valley below the bridge. (a) how much time does it take
gregori [183]
Refer to the diagram shown below.

When the bolt is dropped at a height of 94 m, its initial velocity, V, is zero.
The last 26% of its fall is at a height of 0.26*94 = 24.4 m.
At that time, the bolt has fallen by 94 - 24.4 = 69.56 m.

The time, t, for the bolt to fall a known distance obeys the equation 
s = Vt + (1/2)gt²,
where
s = 69.56 m, vertical distance traveled, and
g = acceleration due to gravity.

Therefore
69.56 = 0 + (1/2)*9.8*t²
t² = (69.56*2)/9.8
t = 3.7677 s

The total time, T, to fall 94 m is given by 
94 = (1/2)*9.8*T^2
T² = 19.1837
T = 4.38 s

The time taken to pass through the last 26% of its fall is
T - t = 4.38 - 3.7677 = 0.6122 s

The speed after falling 69.56 m is given by
V₁ = 0 + g*t = 36.9235 m/s

The speed with which the bolt strikes the ground is given by
V₂ = 0 +g*T = 9.8*4.38 = 42.924 m/s

Answer:
(a) The bolt takes 0.6122 s to pass through the last 26% of its fall.
(b) When the bolt begins the last 26% of its fall, its speed is 36.92 m/s (nearest hundredth).
(c) Just before it strikes the ground, the speed of the bolt is 42.94 m/s (nearest hundredth).

8 0
3 years ago
3) A dock worker pushes a 72 kg crate up a 2.0 m high,
Vlad [161]

Work done on the crate is 1411.2 J

Explanation:

Work done is defined as the product of force and the distance moved by the object. The unit of work done is in joules and denoted by the symbol J.

                                     Work done = F * d

where F represents the force and d represents the distance moved by the object.

mass = 72 kg , distance moved by the object is given by 2.0 m

Force F = mass * gravity = 72 * 9.8

             = 705.6 N =706 N.

Work done = 706 * 2.0 = 1412 J.

                   

7 0
3 years ago
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