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kifflom [539]
3 years ago
15

A ball initially at rest is dropped from an unknown height. Right before the ball hits the ground, it reaches a velocity of 30 m

/s. Assuming air resistance is negligible, calculate the initial height of the object.
A.
15 m
B.
30 m
C.
45 m
D.
75 m
Physics
1 answer:
zzz [600]3 years ago
5 0

Answer:

45m

Explanation

Using third equation of motion which's vf^2 - vi^2 = 2gh in case of vertical motion so ,

step 1 : (30)^2 - (0)^2 =  2(10) h

step 2 : 900 = (20)h

step 3 : 900/20 = h

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Answer:

The Heavier Firefighter

Explanation:

Generally, more massive objects will have more intertia than less massive objects.  As such it takes more force to halt a more massive object if its moving at the same speed as a smaller object. This can also be thought of in the context of Newton's second law. The more force needed to accelerate an object means the more force the object will have.

6 0
3 years ago
How much heat is needed to change the temperature of 3 grams of gold (c = 0.129 ) from 21°C to 363°C? The answer is expressed to
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Q= mcΔT

Where Q is heat or energy

M is mass, c is heat capacitance and t is temperature

You have to convert Celsius into kelvin in order to use this formula I believe

Celsius + 273 = Kelvin

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363 + 273 = 636K

Now...

Q= (0.003)(0.129)(636-294)

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3 0
3 years ago
Read 2 more answers
If a steady-state heat transfer rate of 3 kW is conducted through a section of insulating material 1.0 m2 in cross section and 2
kaheart [24]

Answer:

\Delta T = \frac{3000 W *0.025 m}{1 m^2 (0.2 \frac{W}{mK})}= 375 K

So then the difference of temperature across the material would be \Delta T = 375 K

Explanation:

For this case we can use the Fourier Law of heat conduction given by the following equation:

Q = -kA \frac{\Delta T}{\Delta x}   (1)

Where k = thermal conductivity = 0.2 W/ mK

A= 1m^2 represent the cross sectional area

Q= 3KW represent the rate of heat transfer

\Delta T is the temperature of difference that we want to find

\Delta x=2.5 cm =0.025 m represent the thickness of the material

If we solve \Delta T in absolute value from the equation (1) we got:

\Delta T =\frac{Q \Delta x}{Ak}

First we convert 3KW to W and we got:

Q= 3 KW* \frac{1000W}{1 Kw}= 3000 W

And we have everything to replace and we got:

\Delta T = \frac{3000 W *0.025 m}{1 m^2 (0.2 \frac{W}{mK})}= 375 K

So then the difference of temperature across the material would be \Delta T = 375 K

5 0
4 years ago
A combined circuit has two resistors in series (27.5 ohms and 33.0 ohms) and another in parallel (22.0 ohms). If the power sourc
Dafna1 [17]
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