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3 years ago

What does a chemial formula represent

Physics

1 answer:

Tcecarenko [31]3 years ago

5 0

Answer:

A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus and minus signs.

Explanation:

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If position vector r = bt^2i + ct^3j, where b and c are positive constants, when does the velocity vector make an angle of 450 w

vazorg [7]

$\vec r(t)=bt^2\,\vec\imath+ct^3\,\vec\jmath$

The velocity at time $t$ is

$\dfrac{\mathrm d\vec r(t)}{\mathrm dt}=2bt\,\vec\imath+3ct^2\,\vec\jmath$

Take two vectors that point in the positive $x$ and positive $y$ directions, such as $\vec\imath$ and $\vec\jmath$ . The dot products of the velocity vector with $\vec\imath$ and $\vec\jmath$ are

$\dfrac{\mathrm d\vec r(t)}{\mathrm dt}\cdot\vec\imath=2bt=\sqrt{4b^2t^2+9c^2t^4}\cos\theta$

and

$\dfrac{\mathrm d\vec r(t)}{\mathrm dt}\cdot\vec\jmath=3ct^2=\sqrt{4b^2t^2+9c^2t^4}\cos\theta$

We want the angles between these vectors to be 45º, for which we have $\cos45^\circ=\frac1{\sqrt2}$ . So

$\begin{cases}2\sqrt2\,bt=\sqrt{4b^2t^2+9c^2t^4}\\3\sqrt2\,ct^2=\sqrt{4b^2t^2+9c^2t^4}\end{cases}\implies3\sqrt2\,ct^2-2\sqrt2\,bt=0$

$\implies t(3ct-2b)=0$

$\implies t=0\text{ or }t=\dfrac{2b}{3c}$

When $t=0$ , the velocity vector is equal to the zero vector, which technically has no direction/doesn't make an angle with any other vector. So the only time this happens is for

$\boxed{t=\dfrac{2b}{3c}}$

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3 years ago

Why is it important to keep the muzzle of a firearm pointed in a safe direction, even though the firearm's safety is engaged?

Gnom [1K]

The correct answer is B. The safety only prevents you from pulling the trigger, but does not stop the pin from striking the primer. For example, if you drop the firearm, the pin may hit the primer and fire the firearm. It is always responsible to keep the firearm pointed in a safe direction so that if this happens, no consequences come out of it.

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3 years ago

A steel ball and a piece of clay have equal mass. They are dropped from the same height on a horizontal steel platform. The ball

emmasim [6.3K]

Answer: The ball (option A)

Explanation: change in momentum is defined by the formulae m(v - u) where m = mass of object, v = final velocity and u = initial velocity.

For the ball, it hits the ground and bounces back with the same speed, that's final velocity equals initials (v = - u)

Change in momentum = m( -u- u) = m(-2u) = m(-2u) = -2mu

For the clay, it final velocity is zero since it sticks to the floor, hence (v =0)

m(v - u) = m(0 - u) = - mu.

-2mu (change in momentum from the ball) is greater than - mu ( change in momentum of clay)

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3 years ago

What is the scientific law?

storchak [24]

Answer:

Explanation:

A scientific law is the statement which is based on the repeated experimental trials and observations. The scientific law is abide by the scientific community and major research are based on this. The content or information of scientific law cannot be changed.

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3 years ago

Light of wavelength O is passed through a diffraction grating with N lines/meter and then lands on a screen a distance L from th

rodikova [14]

Condition for diffraction

$dsin\theta = m\lambda$