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katovenus [111]

3 years ago

9

A rock rolls down a steep hill. Its intial velocity is 1 meter per second. By the time it reaches the bottom of the hill 30 seco

nds later. Its velocity is 7 meters per second. What is the acceleration of the rock

1 answer:

Andru [333]3 years ago

7 0

2 meters per second is the answer

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A 47.2 kg girl is standing on a 177 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a flat,

Softa [21]

Answer:

v_g,i = 1.208 m/s

Explanation:

We are given;

Mass of girl; m_g = 47.2 kg

Mass of plank; m_p = 177 kg

Let the velocity of girl to ice be v_g,i

Let the velocity of plank to ice be v_p,i

Since the velocity of the girl is 1.53 m/s relative to the plank, then;

v_g,i + v_p,i = 1.53

From conservation of momentum;

m_g × v_g,i = m_p × v_p,i

Thus;

47.2(v_g,i) = 177(v_p,i)

Dividing both sides by 47.2 gives;

v_g,i = 3.75(v_p,i)

v_pi = (v_g,i)/3.75

Thus, from v_g,i + v_p,i = 1.53, we have;

v_g,i + ((v_g,i)/3.75) = 1.53

v_g,i(1 + 1/3.75) = 1.53

1.267v_g,i = 1.53

v_g,i = 1.53/1.267

v_g,i = 1.208 m/s

5 0

3 years ago

In the semi arid regions of China, the country's inhabitants have practiced water harvesting for generations. Water harvesting i

lapo4ka [179]

Answer: C) By collecting run off during the rainy season for future irrigation increases the agricultural production

Explanation:

Water harvesting is a process of collection of rain water by using special water storing systems. This water storage practice helps during the scarcity of water like in dry summer seasons and in conditions of drought. Such water can be treated with filters to make it potable for drinking. But generally the water is used for the purpose of irrigation in the agricultural field and household sanitary requirements.

On the basis of the above description, By collecting run off during the rainy season for future irrigation increases the agricultural production is the correct option.

3 0

3 years ago

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Stirring dry yeast into a bowl of hydrogen peroxide causes bubbles to form. Blowing air into a glass of milk with a straw also c

Firdavs [7]

The first sentence is a chemical change because it is two component's that when mixed together you make bubbles and the second one is physical because you are making the bubbles cause just setting the straw in there is just doing nothing

4 0

2 years ago

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To create "dry ice," manufacturers compress and cool carbon dioxide gas until it solidifies. Describe what happens to the carbon

tester [92]

Answer:

Explanation:

Temperature is defined as the average kinetic energy of the molecules of a substance. When a substance is cooled, the average kinetic energy of its molecules is reduced tremendously. Thus, the molecules of the substance no longer move at high speeds.

Gases, according to the ideal theory of gas molecules do not associate but are infinitely free and move at very high speeds. However, when cooled, the kinetic energy of these molecules become sufficiently low so as to allow intermolecular association. Secondly, compressing the carbon dioxide gas increases the pressure and decreases its volume. This further makes the carbon dioxide molecules to associate more rapidly. Since dry ice is sublime, CO2 doesn't pass through a liquid state, rather a highly ordered solid-state called dry ice is formed.

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2 years ago

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A 10 m long steel beam is accidentally dropped by a construction crane from a height of 4.89 m. The horizontal component of the

Otrada [13]

Answer:

e = 1.21 mV

Explanation:

given,

length of rod = 10 m

height of drop = 4.89 m

Earth’s magnetic field = 12.4 µT

acceleration of gravity = 9.8 m/s²

velocity of the beam

$v = \sqrt{2gh}$

$v = \sqrt{2\times 9.8 \times 4.89}$

v = 9.79 m/s

emf of the beam

e = B l v

e = 12.4 x 10⁻⁶ x 9.79 x 10

e = 1.21 x 10⁻³ V

e = 1.21 mV

4 0

3 years ago