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Alinara [238K]
3 years ago
13

An airplane of mass 1.60 ✕ 104 kg is moving at 66.0 m/s. The pilot then increases the engine's thrust to 7.70 ✕ 104 N. The resis

tive force exerted by air on the airplane has a magnitude of 5.00 ✕ 104 N. (a) Is the work done by the engine on the airplane equal to the change of the airplane's kinetic energy after it travels through some distance through the air? Yes No Correct: Your answer is correct. Is the mechanical energy conserved? Explain your answer. Energy is not conserved because there is friction. (b) Find the speed of the airplane after it has traveled 5.00 ✕ 102 m. Assume that the airplane is in level flight throughout the motion.
Physics
1 answer:
Ivan3 years ago
8 0

(a) No, because the mechanical energy is not conserved

Explanation:

The work-energy theorem states that the work done by the engine on the airplane is equal to the gain in kinetic energy of the plane:

W=\Delta K (1)

However, this theorem is only valid if there are no non-conservative forces acting on the plane. However, in this case there is air resistance acting on the plane: this means that the work-energy theorem is no longer valid, because the mechanical energy is not conserved.

Therefore, eq. (1) can be rewritten as

W=\Delta K + E_{lost}

which means that the work done by the engine (W) is used partially to increase the kinetic energy of the airplane (\Delta K) and part is lost because of the air resistance (E_{lost}).

(b) 77.8 m/s

First of all, we need to calculate the net force acting on the plane, which is equal to the difference between the thrust force and the air resistance:

F=7.70\cdot 10^4 N - 5.00 \cdot 10^4 N=2.70\cdot 10^4 N

Now we can calculate the acceleration of the plane, by using Newton's second law:

a=\frac{F}{m}=\frac{2.70\cdot 10^4 N}{1.60\cdot 10^4 kg}=1.69 m/s^2

where m is the mass of the plane.

Finally, we can calculate the final speed of the plane by using the equation:

v^2- u^2 = 2aS

where

v=? is the final velocity

u=66.0 m/s is the initial velocity

a=1.69 m/s^2 is the acceleration

S=5.00 \cdot 10^2 m is the distance travelled

Solving for v, we find

v=\sqrt{u^2+2aS}=\sqrt{(66.0 m/s)^2+2(1.69 m/s^2)(5.00\cdot 10^2 m)}=77.8 m/s

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3000 hurs

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The drum of a washing machine spins at 200 rpm the drum had a radius of 0.5m what will the centripetal force experienced by a to
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The centripetal force experienced by the towel is 55 N.

The given parameters;

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  • radius of the machine' drum, r = 0.5 m
  • mass of the towel, m = 0.25 kg

The centripetal force experienced by the towel spinning along the walls of the drum is calculated as follows;

Fc = mrω²

where;

<em>Fc is the centripetal force</em>

<em>ω is angular speed in rad/s</em>

The angular speed in rad/s is calculate as;

\omega = \frac{200 \ rev}{\min} \times \frac{2\pi \ rad}{1 \ rev} \times \frac{1\min}{60 \ s} \\\\\omega = 20.95 \ rad/s

The centripetal force experienced by the towel is calculated as;

F_c = mr\omega ^2\\\\F_c = 0.25 \times 0.5 \times (20.95)^2\\\\F_c = 54.9 \ N \ \approx 55 \ N

Thus, the centripetal force experienced by the towel is 55 N.

Learn more here: brainly.com/question/20905151

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3 years ago
A decrease in the magnitude of velocity is called
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Any change in the speed or direction of motion is called "acceleration". You'll hear "deceleration" used for slowing down but that's not technically correct.
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If the electric field of an electromagnetic wave is in the x-direction and the magnetic field of the wave is in the y-direction,
Ulleksa [173]

Answer:

Positive z-direction

Explanation:

According to Fleming's right hand rule, point the fingers of your right hand in the direction of Electric field E ( positive x-direction), and curl your fingers toward magnetic field B (positive y-direction), and your thumb points in the direction of propagation of wave (positive z-direction).

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In an electricity experiment, a 1.20 g plastic ball is suspended on a 59.0 cm long string and given an electric charge. A charge
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Answer:

a.) 5.24 10⁻³ N . b) 0.013 N

Explanation:

a) In absence of other forces, the plastic ball is only subject to the force of gravity (downward) , and to the tension in the string, which are equal each other.

We are told that there exists an horizontal force , of an electric origin, that causes the ball to swing out to a 24º angle (respect the normal) and remain there, so there exists a new equilibrium condition.

In this situation, both the vertical and horizontal components of the external forces acting on the ball (gravity, tension and the electrical force) must be equal to 0.

The only force that has horizontal and vertical components, is the tension in the string.

We can apply Newton's 2nd Law to both directions, as follows:

T cos 24º - mg = 0

-T sin 24º + Fe = 0

where T= Tension in the string.

Fe = Electrical Force

mg = Fg = gravity force

⇒ T = mg/ cos 24º

Replacing in the horizontal forces equation:

-mg/cos 24º . sin 24º = -Fe

∴ Fe = mg. tg 24º = 0.0012 kg. 9.8 m/s². tg 24º = 5.24 10⁻³ N

b) In order to get the value of T, we can simply solve for T the vertical forces component equation , as follows:

T = mg/ cos 24º = 0.0012 kg. 9.8 m/s² / 0.914 = 0.013 N

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2 years ago
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