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3 years ago

A person is running on a track. Which of the following forces propels the runner forward?

Physics

1 answer:

Naddika [18.5K]3 years ago

5 0

Answer:

The way that runners propel themselves is because of Newton's Third Law. The normal force by the feet on the ground create an equal and opposite force to propel the runner forward.

Explanation:

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You attach a 3.10 kg weight to a horizontal spring that is fixed at one end. You pull the weight until the spring is stretched b

dolphi86 [110]

Answer:

0.785 m/s

Explanation:

Hi!

To solve this problem we will use the equation of motion of the harmonic oscillator, i.e.

$x(t) = A cos(\omega t )+B sin(\omega t)$ - (1)

$\frac{dx}{dt}(t) = \omega (B cos(\omega t )- A sin(\omega t)$ - (1)

The problem say us that the spring is released from rest when the spring is stretched by 0.100 m, this condition is given as:

$x(0) = 0.100$

$\frac{dx}{dt}(0) = 0$

Since cos(0)=1 and sin(0) = 0:

$x(0)=A$

$\frac{dx}{dt}(0) = -B\omega$

We get

$A =0.100\\B = 0$

Now it say that after 0.4s the weigth reaches zero speed. This will happen when the sping shrinks by 0.100. This condition is written as:

$x(0.4) = - 0.100$

Since

$x(t) = 0.100 cos(\omega t)\\ -0.100=x(0.4)=0.100cos(\omega 0.4)$

This is the same as:

$-1 = cos(0.4\omega)$

We know that cosine equals to -1 when its argument is equal to:

(2n+1)π

With n an integer

The first time should happen when n=0

Therefore:

π = 0.4ω

ω = π/0.4 -- (2)

Now, the maximum speed will be reached when the potential energy is zero, i.e. when the sping is not stretched, that is when x = 0

With this info we will know at what time it happens:

$0 = x(t) = 0.100cos(\omega t)$

The first time that the cosine is equal to zero is when its argument is equal to π/2

i.e.

$t_{maxV}=\pi /(2\omega)$

And the velocity at that time is:

$\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\omega t_{maxV})\\\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\pi/2)\\$

But sin(π/2) = 1.

Therefore, using eq(2):

$\frac{dx}{dt}(t_{maxV} ) = 0.100*\omega = 0.100\frac{\pi}{0.400} = \pi/4$

And so:

$V_{max} = \pi / 4 =0.785$

6 0

3 years ago

Match these items. 1. Ca 6 proton 2. H 2O 3 fission 3. nuclear decay 7 element 4. nuclear synthesis 8 electron 5. η atomic numbe

Gnesinka [82]

1. Ca → Element

2. Proton → positive

3. H2O → compound

4. Fission → nuclear decay

5. Fusion → Nuclear synthesis

6. η → Neutron

7. e → electron

8. Atomic number → no of protons in nucleus.

Explanation

1. Ca (Calcium):

Calcium is an element with the atomic number of 20. It is an alkaline earth metal. The 99% of calcium is found in our bodies, in bones, teeth.

2. Proton:

Proton is a subatomic particle and it holds the positive charge. Proton is present in the nucleus of the atom.

3. H2O (water):

Water is a chemical compound and it's chemical formula is H2O. It's called compound as it contains 2 hydrogen and 1 oxygen atoms bonded together through the covalent bond.

4. Fission:

Fission is a process in which large massive unstable nucleus splits into the smaller, less heavier and stable nuclei. The energy is re;eased in the form of radiations during this process. It's called as the radioactive decay.

5. Fusion:

Fusion is opposite of the fission reaction. As in this case the two nuclei combines to form a single large nucleus. That's why it is a nuclear synthesis process.

6. η neutron:

Neutron is a subatomic particle and it is a neutral particle which is located inside the nucleus. n is a symbol used for the neutron.

7. e Electron:

The symbol for electron is e. It's a subatomic particle with negative charge. It is found in the orbits around the nucleus.

8. Atomic Number:

Atomic number is defined as the number of protons in the nucleus of an atom. IT is represented by Z.

6 0

3 years ago

Choose the four major environmental

creativ13 [48]

B that’s the answer your welcome

6 0