(03.02 LC)

A 5-kg projectile is fired over level ground with a velocity of 200 m/s at an angle of 25°above the horizontal. Just before it h

Nutka1998 [239]

Answer:

the change in thermal energy of the projectile is 43.8 kJ

Explanation:

Given;

mass of the object, m = 5kg

initial velocity of the projectile, v₁ = 200 m/s

final velocity of the projectile, v₂ = 150 m/s

To determine the the change in the thermal energy of the projectile and air, we consider change in potential and kinetic enrgy of the projectile. Since the projectile was fired over level ground, change in potential energy is zero.

Then, change in thermal energy of the projectile, KE = Δ¹/₂mv²

KE = Δ¹/₂mv² = ¹/₂m(v₁²-v₂²)

KE = ¹/₂ × 5(200²-150²) = 2.5(17500) = 43750 J = 43.8 kJ

Therefore, the change in thermal energy of the projectile is 43.8 kJ

8 0

3 years ago

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Dario, a prep cook at an Italian restaurant, spins a salad spinner and observes that it rotates 20.0 times in 5.00 seconds and t

BabaBlast [244]

Answer:

$-\frac{8\pi}{3}rad/s^2$

Explanation:

To solve this problem we need to apply the concept related to Angular Acceleration. We can find it through the equation

$\omega_f^2-\omega_i^2=2\alpha\theta$

Where for definition,

$\omega_i = \frac{\theta}{t}$

The number of revolution $(\theta)$ was given by 20 times, then

$\omega_i = \frac{20*2pi}{5}$

$\omega = 8\pi rad/s$

We know as well that the salad rotates 6 more times, therefore in angle measurements that is

$\theta = 6*2\pi rad = 12\pi rad$

The cook at the end stop to spin, then using our first equation,

$0-8\pi = 2\alpha (12\pi)$

re-arrange to solve $\alpha$ ,

$\alpha = \frac{-8\pi}{2*12\pi}$

$\alpha = -\frac{8\pi}{3}rad/s^2$

We can know find the required time,

$\omega_f-\omega_i = \alpha t$

Re-arrange to find t, and considering that $\omega_f=0$

$t= \frac{\omega_i}{\alpha}$

$t=\frac{-8\pi}{-8\pi/3}$

$t=3s$

Therefore take for the salad spinner to come to rest is 3 seconds with acceleration of $-\frac{8\pi}{3}rad/s^2$

6 0

3 years ago

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A crane motor exerts 3,500.0 W to lift a load up 5 floors in 25.0 seconds. The crane did how much J of work.

sertanlavr [38]

Answer:

87,500 J

Explanation:

Power = energy / time

3,500.0 W = E / 25.0 s

E = 87,500 J

6 0

3 years ago

A nuclear power plant generates 3000 MW of heat energy from nuclear reactions in the reactor's core. This energy is used to boil

kondaur [170]

Answer:

a) $\eta_{th} = 46.1\,\%$ , b) $\eta_{th,real} = 36.667\,\%$

Explanation:

a) The maximum possible thermal efficiency of the power plant is given by the Carnot's Cycle thermal efficiency, which consider a reversible power cycle according to the Second Law of Thermodynamics, whose formula is:

$\eta_{th} = \left(1-\frac{T_{L}}{T_{H}} \right)\times 100\,\%$

Where:

$T_{L}$ - Temperature of the cold reservoir (Condenser), measured in K.

$T_{H}$ - Temperature of the hot reservoir (Evaporator), measured in K.

The maximum possible thermal efficiency is:

$\eta_{th} = \left(1-\frac{298.15\,K}{553.15\,K} \right)\times 100\,\%$

$\eta_{th} = 46.1\,\%$

b) The actual efficiency of the plant is the ratio of net power to input heat rate expressed in percentage:

$\eta_{th, real} = \frac{\dot W}{\dot Q_{in}} \times 100\,\%$

$\eta_{th, real} = \frac{1100\,MW}{3000\,MW}\times 100\,\%$

$\eta_{th,real} = 36.667\,\%$

8 0

3 years ago

Help pls it’s urgent

vaieri [72.5K]

Answer:

decreases, but frequency increases.

Explanation:

Wavelength and frequency are inversely proportional, meaning the higher the frequency, the shorter the wavelength, and the lower the frequency, the longer the wavelength.

4 0

2 years ago