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3 years ago

Which of the following changes will always increase the efficiency of a thermodynamic engine? Choose all correct statements.

Physics

2 answers:

slava [35]3 years ago

6 0

Answer:

option (c)

Explanation:

The efficiency of the engine is given by

$\eta =1-\frac{T_{c}}{T_{H}}$

to increase the efficiency of the engine, the temperature of the cold reservoir should be decreased and thus the temperature of hot reservoir be increased.

So, decrease the ratio of Tc/TH.

option (C)

Ilya [14]3 years ago

5 0

Answer:B,C,D

Explanation:

Thermodynamic efficiency is given by

$\eta =1-\frac{T_C}{T-H}$

$\eta$ efficiency can be increased by Keeping $_c$ constant and increasing $T_H$

Keeping $T_H$ constant and decreasing $T_c$

by increasing $\Delta T=T_H-T_c$

by decreasing $\frac{T_C}{T_H}$ ratio

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Find the gravitational potential energy of an 84 kg person standing atop Mt. Everest at an altitude of 8848 m. Use sea level as

djverab [1.8K]

Answer:

$E=7.28\times 10^6\ J$

Explanation:

Given that,

Mass of a person, m = 84 kg

The person is standing at a top of Mt. Everest at an altitude of 8848 m

We need to find the gravitational potential energy of the person. We know that the gravitational potential energy is possessed due to the position of an object. It is given by :

E = mgh, g is the acceleration due to gravity

$E=84\ kg\times 9.8\ m/s^2\times 8848\ m\\\\E=7283673.6\ J\\\\E=7.28\times 10^6\ J$

So, the gravitational potential energy of the person is $7.28\times 10^6\ J$

6 0

3 years ago

A steel beam of mass 1975 kg and length 3 m is attached to the wall with a pin that can rotate freely on its right side. A cable

Nuetrik [128]

Answer:

a) 29062.125 N·m

b) 0 N·m

c) $Torque, due \ to \ tension =L\cdot Tsin\theta = \frac{M\cdot L\cdot g}{2}$

d) T = 11186.02 N

Explanation:

We are given

Beam mass = 1975 kg

Beam length = 3 m

Cable angle = 60° above horizontal

a) We have the formula for torque given as follows;

Torque about the pin = Force × Perpendicular distance of force from pin

Where the force = Force due to gravity or weight, we have

Weight = Mass × Acceleration due to gravity = 1975 × 9.81 = 19374.75 N

Point of action of force = Midpoint for a uniform beam = length/2

∴ Point of action of force = 3/2 = 1.5 m

Torque due to gravity = 19374.75 N × 1.5 m = 29062.125 N·m

b) Torque about the pinned end due to the contact forces between the pin and the beam is given by the following relation;

Since the distance from pin to the contact forces between the pin and the beam is 0, the torque which is force multiplied by perpendicular distance is also 0 N·m

c) To find the expression for the tension force, T we find the sum of the moment forces about the pin as follows

Sum of moments about p is given as follows

∑M = 0 gives;

T·sin(θ) × L= M×L/2×g

Therefore torque due to tension is given by the following expression

$Torque, due \ to \ tension =L\cdot Tsin\theta = \frac{M\cdot L\cdot g}{2}$

d) Plugging in the values in the torque due to tension equation, we have;

$3\times Tsin60 = \frac{1975\times 3\times 9.81}{2} = 29062.125$

Therefore, we make the tension force, T the subject of the formula hence

$T= \frac{29062.125}{3 \times sin(60)} = 11186.02 N$

8 0

3 years ago

When an object reflects all the light waves that strike it looks white or black?

egoroff_w [7]

Light waves can be from any color, depends on what it is bouncing no or reflecting off of.

3 0

3 years ago

A constant friction force of 25 N acts on a 65-kg skier for 15 s on level snow. What is the skier’s change in velocity

nikdorinn [45]

Answer:

$\Delta v=5.77m/s$

Explanation:

Newton's 2nd Law relates the net force F on an object of mass m with the acceleration a it experiments by F=ma. In our case the net force is the friction force, since it's the only one the skier is experimenting horizontally and the vertical ones cancel out since he's not moving in that direction. Our acceleration then will be:

$a=\frac{F}{m}$