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3 years ago

Give an example of Newton's first law of

1 answer:

4 0

Answer: If you slide a hockey puck on ice, eventually it will stop, because of friction on the ice. It will also stop if it hits something, like a player's stick or a goalpost.

Explanation:

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Energy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is one kilocalorie, defined as 1 kc

Sergeeva-Olga [200]

Answer:

a) The student must run flight of stairs to lose 1.00 kg of fat 709.5 times.

b) Average power

P(w)= 1062.07 [w]

P(hp)=1.42 [hp]

c) This activity is highly unpractical, because the high amount of repetitions he has to due in order to lose, just 1 Kg of fat.

Explanation:

First, lets consider the required amount of work to move the mass of the student. (considering running stairs just as a vertical movement)

Work:

$W= F*d= m*g*d$

Where m is the mass of the student, g is gravity (9.8 m/s) and d is the total distance going up the stairs (0.15m *85steps= 12.75m )

$W= F*d= m*g*d=85* 9.8*12.75=10620.75 [J]$

Converting from Joules to Kcals:

$\frac{10620.75}{4186} =2.537 Kcal$

Now lets take into account the efficiency of the human body (20%)

2.537 ---> 20%

x ---> 100%

$x=\frac{2.537*100}{20} =12.685$

So the student is consuming 12.685 KCals each time he runs up the stairs.

Now,

1 g --> 9 Kcals

1000 g --> 9000KCals

Burning 1 g of fat, requieres 9 KCals, 1000g burns 9000KCals. So in order to burn a 1Kg of fat:

$\frac{9000Kcals}{12.685Kcals} =709.5 times$

He must run up the stairs 709.5 times, to burn 1 Kg of fat.

********************

For b) just converting units, taking into account the time lapse. (53103.75 is the 100% of the energy in joules, from converting 12.685Kcals to joules)

$Power=\frac{Joules}{Seconds} =\frac{53103.75}{50} =1062.075 [W]\\$

$P(hp)=\frac{P(w)}{745.7} =\frac{1062.075}{745.7} =1.42[hp]$

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4 0

4 years ago

Which substance cannot be seperated physically or chemically?

scoray [572]

Answer:

What is a Pure Substance?

Explanation:

It is something which cannot be divided into parts by physical means, as it's all made up of the same thing. Pure substances are either elements or compounds. Elements can NOT be separated into other types of matter (physically or chemically).

4 0

3 years ago

Read 2 more answers

A force of 150 N is used to push a motorcycle 10 m along a road in 20 s.

Grace [21]

Answer:

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7 0

3 years ago

Which of the following statements is/are true? Check all that apply. Check all that apply. The total mechanical energy of a syst

Taya2010 [7]

Answer:

1) True, 2) True, 3) False, 4) False, 5) False

Explanation:

1) True. Dissipative energy cannot be recovered, in general it is a form of heat

2) True. The dissipation can be by radiation, heat

3) False. Mechanical energy is divided into K and U but not in equal parts

4) False. When there are dissipative interactions, part of the mechanical energy is set in the form of heat, so its value decreases

5) False. Mechanical energy is the sum of those two energies

8 0

3 years ago

A diode vacuum tube consists of a cathode and an anode spaced 5-mm apart. If 300 V are applied across the plates. What is the ve

MAXImum [283]

Answer:

Explanation:

There is electric field between the plates whose value is given by the following expression

electric field E = V /d where V is potential between the plates and d is distance between them

E = 300 / 5 x 10⁻³

= 60 x 10³ N/c

Force on electron = q E where q is charge on the electron

F = 1.6 X 10⁻¹⁹ X 60 X 10³ = 96 X 10⁻¹⁶ N.

Acceleration a = force / mass

a = 96 x 10⁻¹⁶/ mass = 96 x 10⁻¹⁶ / 9.1 x 10⁻³¹

= 10.55 x 10¹⁵ m / s²

For midway , distance travelled

s = 2.5 x 10⁻³ m

s = 1\2 a t²

t = $\sqrt{\frac{2s}{a\\ } }$

= $\sqrt{\frac{2\times2.5\times10^{-3}}{ 10.55\times10^{15}}$

t = .474 x 10⁻¹⁸ s

For striking the plate time is calculated as follows

t = $[tex]\sqrt{\frac{2\times5\times10^{-3}}{ 10.55\times10^{15}}$ [/tex]

t = 0.67 x 10⁻¹⁸ s

3 0

3 years ago