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o-na [289]
3 years ago
6

A car travels 70 km in two hours 104 km in the next 1.5 hours and then 79 km in two hours before reaching its destination what w

as the cars average speed?
Physics
1 answer:
stiks02 [169]3 years ago
4 0

Average speed = (total distance) / (total time)

Total distance = (70km + 104km + 79km) = 253 km

Total time = (2hr + 1.5hr + 2hr) = 5.5 hrs

Average speed = (253 km) / (5.5 hrs)

<em>Average speed = 46 km/hr</em>

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An engine that has an efficiency of 25% takes in 200 [J] of heat during each cycle. Calculate the amount of work this engine per
BartSMP [9]

Answer:

W=50J

Explanation:

The work done W and the energy taken Q_{in} by a heat engine are related to the efficiency \eta by the expression

\eta=\frac{W}{Q_{in}}

The efficiency is \eta=25%, the numerical form of this percentage is 0.25 and the energy taken is Q_{in}=200J. Replacing in the formula:

0.25=\frac{W}{200}\\W=200*0.25\\W=50J

5 0
3 years ago
Expectant mothers many times see their unborn child for the first time during an ultrasonic examination. In ultrasonic imaging,
katrin2010 [14]

Answer:

<em>380 kHz</em>

<em></em>

Explanation:

The speed of sound is taken as 1500 m/s

The length of the fetus is 1.6 cm long

The condition is that the wavelength used must be at most 1/4 of the size of the object that is to be imaged.

For this 1.6 cm baby, the wavelength must not exceed

λ = \frac{1}{4} of 1.6 cm = \frac{1}{4} x 1.6 cm = 0.4 cm =

0.4 cm = 0.004 m   this is the wavelength of the required ultrasonic sound.

we know that

v = λf

where v is the speed of a wave

λ is the wavelength of the wave

f is the frequency of the wave

f = v/λ

substituting values, we have

f = 1500/0.004 = 375000 Hz

==> 375000/1000 = 375 kHz ≅ <em>380 kHz</em>

4 0
3 years ago
How is the mass number calculated for an element?
natali 33 [55]
<span># of protons + # of neutrons = atomic mass</span>
8 0
4 years ago
A uniformly charged conducting sphere of 1.3 m diameter has a surface charge density of 8.1 µc/m2. (a) find the net charge on th
8_murik_8 [283]
<span>The surface charge density = q/A So q = surface charge density x Area The surface area of a sphere of radius R is 4*Pi*R^2. R = d/2 where d is diameter. This leaves us with 1.3/2 = 0.65. Area = 4 * pie * (0.65)^2 = 5.30998. So the net charge q = 8.1 * 10^(-6) * 5.30998 = 42.47998 * 10^(-6) The Total electric flux = Q/e_0 where , 8.854 Ă— 10â’12, e_0 is permitivity of free space. So Flux = 42.47998 * 10^(-6) / 8.854 * 10(â’12) = 4.833 * 10^(-6 - (-12)) = 4.833 * 10^(6)</span>
8 0
3 years ago
A satellite orbits at a distance from the Earth's center of about 2.60 Earth radii and takes 5.89 hours to go around once. What
Elenna [48]

Answer:

424088766.068 m

Explanation:

Radius of the circular orbit that the satellite is 2.6 Earth radii (r) = 2.6 R

R = Radius of earth = 6371000 m (mean radius)

In order to find the distance that the satellite travels in 5.89 hours to complete one complete revolution is the circumference of the circular orbit

Circumference of a circle = 2×π×r

⇒Distance travelled in 5.89 hours = 2×π×2.6 R

⇒Distance travelled in 5.89 hours = 2×π×2.6×6371000

⇒Distance travelled in 5.89 hours = 104078451.3393m

Distance travelled in 1 hour = 104078451.3393/5.89 = 17670365.252 m

∴ Distance travelled in 24 hours = 17670365.252×24 = 424088766.068 m

5 0
3 years ago
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