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3 years ago

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An object is dropped from rest from a height of 4.1 107 m above the surface of the Earth. If there is no air resistance, what is

its speed when it strikes the Earth

1 answer:

Valentin [98]3 years ago

3 0

Answer:

2.83 x 10^4m/s

Explanation:

First, let us calculate the time taken by the object to hit the surface of the earth.

H = 4.1 x 10^7m

g = 9.8m/s2

t = √(2H/g)

t = √((2x 4.1 x 10^7) /9.8)

t = 2892.64secs

Now, we can find the velocity with which the object strikes the earth as follows:

V = gt

V = 9.8 x 2892.64

V = 2.83 x 10^4m/s

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A model air rocket with a mass of 50.g is free to travel along a horizontal track. It begins from rest. After 2.0s, the rocket h

katen-ka-za [31]

Answer:

$v_r=5.89\ m.s^{-1}$

Explanation:

Given:

mass of rocket, $m_r=50\ g$

time of observation, $t=2\ s$

mass lost by the rocket by expulsion of air, $m_a=10\%\ of m_r=5\ g$

velocity of air, $v_a=53\ m.s^{-1}$

<u>Now the momentum of air will be equal to the momentum of rocket in the opposite direction: </u>(Using the theory of elastic collision)

$m_a.v_a=(m_r-m_a)\times v_r$

$5\times 53=(50-5)\times v_r$

$v_r=5.89\ m.s^{-1}$

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3 years ago

1. Determine the magnitude of two equal but opposite charges if they attract one another with a force of 0.7N when at distance o

adell [148]

Answer:

q = 2.65 10⁻⁶ C

Explanation:

For this exercise we use Coulomb's law

F = $k \frac{q_1q_2}{r^2}$

In this case they indicate that the load is of equal magnitude

q₁ = q₂ = q

the force is attractive because the signs of the charges are opposite

F = $k \ \frac{q^2}{r^2}$

q = $\sqrt{\frac{F \ r^2}{k} }$

we calculate

q = $\sqrt{\frac{0.7 \ 0.3^2 }{9 \ 10^9} }$

q = $\sqrt{7 \ 10^{-12} }$ Ra 7 10-12

q = 2.65 10⁻⁶ C

7 0

3 years ago

This problem follows up on a discussion from lecture. A wind turbine with an efficiency of 45% for converting wind energy into e

Volgvan

Answer:

4.1 m

Explanation:

10 kW = 10000 W

20mi/h = 20*1.6 km/mi = 32 km/h = 32 * 1000 (m/km) *(1/3600) hr/s = 8.89 m/s

The power yielded by the wind turbine can be calculated using the following formula

$P = \frac{1}{2} \rho v^3 A C_p$

where $\rho = 1.2 kg/m^3$ is the air density, v = 8.89 m/s is the wind speed, A is the swept area and $C_p = 0.45$ is the efficiency

$10000 = 0.5 * 1.2 * 8.89^3 * A * 0.45$

$10000 = 190A$

$A = 10000 / 190 = 52.7 m^2$

The swept area is a circle with radius r being the blade length

$\pi r^2 = A = 52.7$

$r^2 = 52.7 / \pi = 16.79$

$r = \sqrt{16.79} = 4.1 m$

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3 years ago

6. A girl pushes her little brother on his sled with a force of 300 N for 750 m.

Oduvanchick [21]

w=225000 J

E=225000 J

P=9000 W

P=22500 W

Ew=Fd=E

P=E/t

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3 years ago

John and Linda are arguing about the definition of density. John says the density of an object is proportional to itsmass. Linda

NeX [460]

Answer:

They are both correct.

Explanation:

The density of an object is defined as the ratio of its mass to its volume. This implies that the density of the object is both proportional to the mass and also to the volume of the object. John only mentioned mass which is correct. Linda mentioned the second variable on which density depends which is the volume of the object.

Hence considering the both statements objectively, one can say that they are both correct.

8 0

3 years ago