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3 years ago

A bus travels 30km in 1/2h. What is it's average speed in km/h

1 answer:

5 0

If a bus travels 30 km in 1/2 hr, then in one hr, he can travel twice the distance.
30*2=60 km

Final answer: 60 km per hr

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Water is boiled at 300 kPa pressure in a pressure cooker. The cooker initially contains 3 kg of water. Once boiling started, it

Inessa [10]

Answer:

The average rate of energy transfer to the cooker is 1.80 kW.

Explanation:

Given that,

Pressure of boiled water = 300 kPa

Mass of water = 3 kg

Time = 30 min

Dryness friction of water = 0.5

Suppose, what is the average rate of energy transfer to the cooker?

We know that,

The specific enthalpy of evaporate at 300 kPa pressure

$h_{f}=561.47\ kJ/kg$

$h_{fg}=2163.8\ kJ/kg$

We need to calculate the enthalpy of water at initial state

$h_{1}=h_{f}$

$h_{1}=561.47\ kJ/kg$

We need to calculate the enthalpy of water at final state

Using formula of enthalpy

$h_{2}=h_{f}+xh_{fg}$

Put the value into the formula

$h_{2}=561.47+0.5\times2163.8$

$h_{2}=1643.37\ kJ/kg$

We need to calculate the rate of energy transfer to the cooker

Using formula of rate of energy

$Q=\dfrac{m(h_{2}-h_{1})}{t}$

Put the value into the formula

$Q=\dfrac{3\times(1643.37-561.47)}{30\times60}$

$Q=1.80\ kW$

Hence, The average rate of energy transfer to the cooker is 1.80 kW.

3 0

3 years ago

Springfield's "classic rock" radio station broadcasts at a frequency of 102.1 mhz. what is the length of the radio wave in meter

Mila [183]

The frequency of the radio wave is:
$f=102.1 MHz = 102.1 \cdot 10^6 Hz$

The wavelength of an electromagnetic wave is related to its frequency by the relationship
$\lambda= \frac{c}{f}$
where c is the speed of light and f the frequency. Plugging numbers into the equation, we find
$\lambda= \frac{3 \cdot 10^8 m/s}{102.1 \cdot 10^6 Hz}= 2.94 m$
and this is the wavelength of the radio waves in the problem.

7 0

3 years ago

If someone is moving at a constant speed of 100 km/h and accelerate to 120km /h in 10 s what is the acceleration

Alex Ar [27]

The acceleration should be a gain of 2 km/h per second

5 0

3 years ago

3. A drill spins with a frequency of 1200 RPM (revolutions per minute). What is its

Damm [24]

Your answer is 20
just take 1,200 divided by 60 [second] :)

6 0

3 years ago