3 years ago

2. David roller skates 15 miles in 75 minutes. What is his average speed in miles per hour? 1

Physics

1 answer:

mestny [16]3 years ago

6 0

I think the answer is 0.2

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The strong force in his body

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An increase in which quantity will result in an increase in momentum?

Mkey [24]

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a. velocity. PLATO USERS

Explanation:

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What is the efficiency of a device that takes in 400 J of heat and does 120 J

777dan777 [17]

The efficiency of the device is 30 %

Explanation:

The efficiency of a heat engine is given by:

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

where

W is the work done by the engine

$Q_{in}$ is the heat in input to the engine

For the device in this problem, we have:

W = 120 J is the work done

$Q_{in} = 400 J$ is the heat in input

Substituting, we find the efficiency:

$\eta=\frac{120}{400}=0.30$

which corresponds to an efficiency of 30%.

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3 years ago

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If a fast-moving car making a loud noise approaches and moves past the person, what will happen as the distance between the two

lesantik [10]

The pitch of the sound of the car will appear to be <span>lower than the pitch of the car next to you</span>

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4 years ago

Planets beyond the solar system.On October 15, 2001, a planet was discovered orbiting around the star HD68988. Its orbital dista

Evgesh-ka [11]

Answer:

Part a)

$M = 2.31 \times 10^{30} kg$

Part b)

$M = 1.15 M_s$

Explanation:

Part a)

As we know that the period of revolution of the planet is given by

$T = 2\pi\sqrt{\frac{r^3}{GM}}$

now we know that

$r = 10.5 \times 10^6 km = 1.05 \times 10^{10} m$

T = 6.3 days

$T = 5.44 \times 10^5 s$

now we have

$5.44 \times 10^5 = 2\pi\sqrt{\frac{(1.05\times 10^{10})^3}{(6.67 \times 10^{-11})M}}$

$M = 2.31 \times 10^{30} kg$

Part b)

As we know that mass of sun is given as

$M_s = 2.0 \times 10^{30} kg$

now we have

$\frac{M}{M_s} = \frac{2.31 \times 10^{30}}{2 \times 10^{30}}$

$M = 1.15 M_s$

6 0

4 years ago