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3 years ago

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Find the net work W done on the particle by the external forces during the motion of the particle in terms of the initial and fi

nal kinetic energies.Express your answer in terms of Kinitial and Kfinal.W=

1 answer:

steposvetlana [31]3 years ago

3 0

Answer:

$W=K_f-K_i$

Explanation:

The work done on a particle by external forces is defined as:

$W=\int\limits^{r_f}_{r_i} {F\cdot dr} \,$

According to Newton's second law $F=ma$ . Thus:

$W=\int\limits^{r_f}_{r_i}{ma\cdot dr} \,\\$

Acceleration is defined as the derivative of the speed with respect to time:

$W=m\int\limits^{r_f}_{r_i}{\frac{dv}{dt}\cdot dr} \,\\\\W=m\int\limits^{r_f}_{r_i}{dv \cdot \frac{dr}{dt}} \,$

Speed is defined as the derivative of the position with respect to time:

$W=m\int\limits^{v_f}_{v_i} v \cdot dv \,$

Kinetic energy is defined as $K=\frac{mv^2}{2}$ :

$W=m\frac{v_f^2}{2}-m\frac{v_i^2}{2}\\W=K_f-K_i$

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Average speed is the total distance divided by the

seraphim [82]

<h2>Answer:</h2>

Time

<h2>Explanation:</h2>

The average speed of an object that is moving is defined as the distance traveled divided by the time of travel. You can measure the distance with a ruler and the time with a stopwatch. This can be expressed as the following formula:

$v=\frac{\Delta x}{\Delta t}$

For instance, if an object travels a distance $\Delta x=100m$ in 4 seconds, the the average speed is:

$v=\frac{100m}{4s} \\ \\ \therefore \boxed{v=25m/s}$

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3 years ago

Explain why water boiling in a container stops<br>boiling momentarily when the lid is removed

Dmitriy789 [7]

Answer:

It's because it tips over the threshold from nucleate boiling, which we can see, to convection boiling, which we can't. ... Even if the steam stayed in the pot, it would still stop boiling when you removed the heat. The steam and water in a liquid/vapour mixture are at the same temperature (100ºC).

Explanation:

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4 years ago

An Air Force plane lands with a velocity of 125 m/s and accelerates at a maximum rate of -6.5 m/s^2.

Alisiya [41]

Answer:

a) 19.2 s

b) No

Explanation:

Given:

v₀ = 125 m/s

a = -6.5 m/s²

v = 0 m/s

a) Find: t

v = at + v₀

(0 m/s) = (-6.5 m/s²) t + (125 m/s)

t ≈ 19.2 s

b) Find: Δx

v² = v₀² + 2aΔx

(0 m/s)² = (125 m/s)² + 2 (-6.5 m/s²) Δx

Δx ≈ 1200 m

An aircraft carrier that's 850 meters long won't be long enough.

8 0

4 years ago

In a physics laboratory experiment, a coil with 200 turns enclosing an area of 13.1 cm2 is rotated during the time interval 3.10

sergij07 [2.7K]

Answer:

A) $\Phi=83.84\times 10^{-9}$

B) $\Phi=0 Wb$

C) $emf=5.4090\times 10^{-4}V$

Explanation:

Given that:

no. of turns i the coil, $n=200$

area of the coil, $a=13.1 \times 10^{-4}\,m^2$

time interval of rotation, $t=3.1\times 10^{-2}\,s$

intensity of magnetic field, $B=6.4\times 10^{-5}\,T$

(A)

Initially the coil area is perpendicular to the magnetic field.

So, magnetic flux is given as:

$\Phi=B.a\,cos \theta$ ..................................(1)

$\theta$ is the angle between the area vector and the magnetic field lines. Area vector is always perpendicular to the area given. In this case area vector is parallel to the magnetic field.

$\Phi=6.4\times 10^{-5}\times 13.1 \times 10^{-4}\, cos 0^{\circ}$

$\Phi=83.84\times 10^{-9} Wb$

(B)

In this case the plane area is parallel to the magnetic field i.e. the area vector is perpendicular to the magnetic field.

∴ $\theta=90^{\circ}$

From eq. (1)

$\Phi=6.4\times 10^{-5}\times 13.1 \times 10^{-4}\, cos 90^{\circ}$

$\Phi=0 Wb$

(C)

According to the Faraday's Law we have:

$emf=n\frac{B.a}{t}$

$emf=\frac{200\times 6.4\times 10^{-5}\times 13.1 \times 10^{-4}}{3.1\times 10^{-2}}$

$emf=5.4090\times 10^{-4}V$

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3 years ago

A ball is ejected to the right with an unknown horizontal velocity from the top of a pillar that is 50 meters in height. At the

dimulka [17.4K]

Answer:

15.67 m/s

Explanation:

The ball has a projectile motion, with a horizontal uniform motion with constant speed and a vertical accelerated motion with constant acceleration g=9.8 m/s^2 downward.

Let's consider the vertical motion only first: the vertical distance covered by the ball, which is S=50 m, is given by

$S=\frac{1}{2}gt^2$

where t is the time of the fall. Substituting S=50 m and re-arranging the equation, we can find t:

$t=\sqrt{\frac{2S}{g}}=\sqrt{\frac{2(50 m)}{9.8 m/s^2}}=3.19 s$

Now we now that the ball must cover a distance of 50 meters horizontally during this time, in order to fall inside the carriage; therefore, the velocity of the carriage should be:

$v=\frac{d}{t}=\frac{50 m}{3.19 s}=15.67 m/s$

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3 years ago