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Irina-Kira [14]
3 years ago
12

Write the answer to this question. Energy is measured in units called joules(J). Suppose a roller coaster car starts with 78,000

J of potential energy. In a few seconds, it converts two-thirds of this energy into kinetic energy. As it takes a curve, the car doubles its kinetic energy. How much mechanical energy does the car now have?
Physics
1 answer:
kolezko [41]3 years ago
7 0

Answer:78,000 J

Explanation:

Given

Initial Potential Energy P=78,000 J=78 kJ

Total Energy=Potential Energy+Kinetic Energy

initially kinetic energy is zero therefore

Total Energy=Potential Energy

If two-thirds of this energy converts to kinetic Energy

i.e. kinetic Energy =\frac{2}{3}\times 78=2\times 26=52 kJ

As it take curve its kinetic Energy doubles i.e.2\times 52=104 kJ

but total Energy is constant i.e. 78 kJ

therefore there must be a decrease in Potential energy of coaster

78=104+P.E.

P.E.=-26 kJ

Mechanical Energy of car is =sum of kinetic and Potential Energy

=78 kJ=78,000 J

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The third option is wrong
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A 1.0-cm-diameter pipe widens to 2.0, then narrows to 0.5. Liquid flows through the first segment at a speed of 4.0. What is the
uysha [10]

Answer:

3.14 ×  10⁻⁴  m³  /s

Explanation:

The flow rate (Q) of a fluid is passing through different cross-sections remains of pipe always remains the same.

Q = Area x velocity

Given:

Diameters of 3 sections of the pipe are given as  

d1  =  1.0  cm,  d2  =  2.0  cm  and  d3  =  0.5  cm.

Speed in the first segment of the pipe is  

v1  =  4  m/s.

From the equation of continuity the flow rate through different cross-sections remains the same.

Flow  rate  =  Q  =  A1  v1  =  A2  v2  =  A3  v3.

Q = A1v1

   =π/4  d²1  v1  =  π/4  * 0.01² ×4.0 m³/s  =  3.14 ×  10⁻⁴  m³  /s

3 0
3 years ago
Water has a mass per mole of 18.0 g/mol, and each water molecule (H20) has 10 electrons. (a) How many electrons are there in one
Allushta [10]

Answer:

total number of electron in 1 litter is 3.34 × 10^{26} electron

Explanation:

given data

mass per mole = 18 g/mol

no of electron = 10

to find out

how many electron in 1 liter of water

solution

we know molecules per gram mole is 6.02 ×10^{23} molecules

no of moles is 1

so

total number of electron in water is = no of electron ×molecules per gram mole × no of moles

total number of electron in water is = 10 × 6.02 ×10^{23} × 1

total number of electron in water is = 6.02×10^{24} electron

and

we know

mass = density × volume    ..........1

here we know density of water is 1000 kg/m

and volume = 1 litter = 1 × 10^{-3} m³

mass of 1 litter = 1000 × 1 × 10^{-3}

mass = 1000 g

so

total number of electron in 1 litter =  mass of 1 litter × \frac{molecules per gram mole}{mass per mole}

total number of electron in 1 litter =  1000 × \frac{6.02*10{24}}{18}

total number of electron in 1 litter is 3.34 × 10^{26} electron

8 0
3 years ago
12.5 Round to the nearest hundredth.
7nadin3 [17]
I think its 13...........
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A truck is moving with a certain uniform velocity. It is accelerated uniformly by 0.75 m/s^2. After 20 seconds , the velocity be
scoundrel [369]

Answer:

Vi = 5 m/s

Explanation:

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a =  -----------

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Vi = Vf - (a * t)  = 20 - (0.75 * 20)

Vi = 5 m/s

5 0
3 years ago
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