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baherus [9]
3 years ago
15

A refrigerator is removing heat from a cold medium at 3∘C at a rate of 5400 kJ/h and rejecting the waste heat to a medium at 30∘

C. If the coefficient of performance of the refrigerator is 2, the power consumed by the refrigerator is
(a) 0.5 kW
(b) 0.75 kW
(c) 1.0 kW
(d) 1.5 kW
(e) 3.0 kW
Physics
1 answer:
ipn [44]3 years ago
3 0

Answer:(b) 0.75 kW

Explanation:

Given

temperature of cold region T_L=3^{\circ}C

Heat removal at the rate of Q_1=5400 kJ/h

temperature of hot region T_H=30^{\circ}C

COP of refrigerator =2

COP of a refrigerator is given by ratio of desired effect to the Power input

COP=\frac{Q_1}{Power}

2=\frac{5400}{P}

P=2700 kJ/h

P=0.75 kW

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A circular hoop of diameter d hangs on a nail. what is the period of its oscillations at small amplitude?
Misha Larkins [42]

m = mass of the circular hoop

r = radius of the hoop

I = moment of inertia of the hoop

moment of inertia of the hoop about the center of hoop is given as

I = m r²

k = distance of the point of suspension from center of mass = r

using parallel axis theorem

I' = moment of inertia of hoop about the point of suspension

I' = I + m k²

I' = m r² + m k²

I' = m r² + m r²

I' = 2 m r²

Time period of oscillation for the hoop is given as

T = 2π sqrt(I'/mgk)

T = 2π sqrt(2 m r²/(mgr))

T = 2π sqrt(2 r/g)

since 2r = diameter = d

T = 2π sqrt(d/g)



4 0
3 years ago
You are an astronaut floating alongside your space ship. If you throw a baseball with a speed of 10 m/s, you will move at:
ZanzabumX [31]

Answer:

D

Explanation:

There is no friction to stop you from moving BC you are in space, however you have a larger mass than the ball, so it takes more force to get you up to the same speed as the baseball. You will move in the opposite direction of the ball because you exerted force on the ball in one direction and therefore yourself in the opposing direction.

4 0
3 years ago
You push a 50 kg wooden box across a wooden floor at a constant speed of 1.0 m/s. The coefficient of kinetic friction is 0.15. N
WARRIOR [948]

Answer:

0.68 seconds

Explanation:

Data provided in the question:

Mass of the box = 50 kg

Speed of the box = 1.0 m/s

Coefficient of friction, μ = 0.15

Now,

Force applied = μmg    

Here,

g is the acceleration due to gravity = 9.8 m/s²

Thus,

F = 0.15 × 50 × 9.8

= 73.5 N

Also,

Force = Mass × Acceleration

thus,

73.5 N = 50 × a

or

a = 1.47 m/s²

After doubling the speed

Final speed = 2 × Initial speed

= 2 × 1 m/s

= 2 m/s

Also,

Acceleration = [change in speed] ÷ Time

or

1.47 = [ 2 - 1 ] ÷ Time

or

Time = 1 ÷ 1.47

or

Time = 0.68 seconds

6 0
4 years ago
How are temperature, pressure, and volume related dealing with the behavior of a gas
fredd [130]
Pressure and volume of a gas are inversely related. As one goes up, the other goes down, and vice-versa. 
7 0
4 years ago
WILL GIVE BRAINLIEST!!where on the HR diagram you would expect to find a supergiant star based on its physical properties.
azamat
It would be on the top of the HR diagram, specifically, the top right. 
5 0
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