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4 years ago

If energy is conserved, why do people get tired , and why are we running short on “energy supplies?”

1 answer:

3 0

Because energy is being consumed. It takes energy to lift things, walk around, etc. We are transferring our chemical energy from meals to our environment and basic functions. The answer to the second part is probably that so much energy has been transferred and stored in our surroundings, and it's difficult to gather that energy into a useful medium for us to use again.

You might be interested in

A mass on a horizontal surface is connected to the spring and pulled to the right along the surface stretching the spring by 25

solniwko [45]

Answer:

320 N/m

Explanation:

From Hooke's law, we deduce that

F=kx where F is applied force, k is spring constant and x is extension or compression of spring

Making k the subject of formula then

$k=\frac {F}{x}$

Conversion

1m equals to 100cm

Xm equals 25 cm

25/100=0.25 m

Substituting 80 N for F and 0.25m for x then

$k=\frac {80}{0.25}=320N/m$

Therefore, the spring constant is equal to 320 N/m

3 0

4 years ago

1. A change in which one or more substances are converted into new substances is a

Ratling [72]

Answer:

CHEMICAL CHANGE:

A change in which one or more substances are converted into new substances is a chemical change.

EXPLANATION:

Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances.

EXAMPLE:

Examples of Chemical Change in Everyday Life

Burning of paper and log of wood.

Digestion of food.

Boiling an egg.

Chemical battery usage.

Electroplating a metal.

Baking a cake.

Milk going sour.

Various metabolic reactions that take place in the cells.

4 0

3 years ago

The spectra of most galaxies show redshifts. this means that their spectral lines _________.

spin [16.1K]

Have wavelengths that are longer than normal.

3 0

3 years ago

A 4g bullet, travelling at 589m/s embeds itself in a 2.3kg block of wood that is initially at rest, and together they travel at

VARVARA [1.3K]

Answer:

The percentage of the kinetic energy that is left in the system after collision to that before is 0.174 %

Explanation:

Given;

mass of bullet, m₁ = 4g = 0.004kg

initial velocity of bullet, u₁ = 589 m/s

mass of block of wood, m₂ = 2.3 kg

initial velocity of the block of wood, u₂ = 0

let the final velocity of the system after collision = v

Apply the principle of conservation of linear momentum

m₁u₁ + m₂u₂ = v(m₁+m₂)

0.004(589) + 2.3(0) = v(0.004 + 2.3)

2.356 = 2.304v

v = 2.356 / 2.304

v = 1.0226 m/s

Initial kinetic energy of the system

K.E₁ = ¹/₂m₁u₁² + ¹/₂m₂u₂²

K.E₁ = ¹/₂(0.004)(589)² = 693.842 J

Final kinetic energy of the system

K.E₂ = ¹/₂v²(m₁ + m₂)

K.E₂ = ¹/₂ x 1.0226² x (0.004 + 2.3)

K.E₂ = 1.209 J

The kinetic energy left in the system = final kinetic energy of the system

The percentage of the kinetic energy that is left in the system after collision to that before = (K.E₂ / K.E₁) x 100%

= (1.209 / 693.842) x 100%

= 0.174 %

Therefore, the percentage of the kinetic energy that is left in the system after collision to that before is 0.174 %

6 0

4 years ago

I would like to know why this is the correct answer

Helen [10]

The acceleration of the object if the net force is decreased = 0.13 m/s²

<h3>Further explanation</h3>

Given

A net force of 0.8 N acting on a 1.5-kg mass.

The net force is decreased to 0.2 N

Required

The acceleration of the object if the net force is decreased

Solution

Newton's 2nd law :

$\tt \sum F=m.a$

The mass used in state 1 and 2 remains the same, at 1.5 kg

state 1

ΣF=0.8 N

m=1.5 kg

The acceleration, a:

$\tt a=\dfrac{\sum F}{m}\\\\a=\dfrac{0.8}{1.5}\\\\a=0.53`m/s^2$

state 2

ΣF=0.2 N

m=1.5 kg

The acceleration, a:

$\tt a=\dfrac{\sum F}{m}\\\\a=\dfrac{0.2}{1.5}\\\\a=0.13~m/s^2$

8 0

3 years ago