Estimate the monthly cost of using a 700-W refrigerator that runs for 10 h a day if the cost per kWh is $0.20.

Factors influencing friction

The magnitude of friction is contingent on the following elements: i) The surface area in contact. ii) The applied pressure on the surfaces. Force is determined by Pressure multiplied by Area; thus, if the contact area increases or if the pressure applied rises, the frictional force will also escalate.

Methods for reducing friction

i) Smooth the contact surface. ii) Apply oil or grease to fill small gaps in flat surfaces. iii) Use ball bearings to minimize contact area among rotating components.

Lubrication

To minimize friction, various methods may be employed: Oil can be either thin or viscous, which depends on its SAE number (SAE indicating Society of Automotive Engineers). Highly viscous oils may not reach all components effectively. In contrast, very thin oils may drain away quickly, resulting in wastage. Grease is preferable in such situations, particularly around ball-bearings. Regular grease or oil should not be utilized under high speed, high pressure, and high temperature conditions—specialized lubricants are required then. The consistency of oil varies with temperature; it thickens in the cold and thins in the heat. Therefore, the choice of lubricant should be seasonally appropriate, and it's always wise to consult the equipment's operating manual prior to making a selection.[[TAG_11]]

<span>E = h x f </span>

<span>Thus: </span>

<span>f = E / h </span>
<span>f = 4.41•10^-19 / 6.62•10^-34 </span>
<span>f = 6.66•10^14 Hz (s^-1) </span>


<span>b/ What is the wavelength of this light? </span>
<span>------------------------------ </span>

<span>λ = c / f </span>
<span>λ = 3•10^8 / 6.66•10^14 </span>
<span>λ = 4.50•10^-7 m </span>

Answer:

The current flowing through the tube is 0.601 A

Explanation:

Given data;

the diameter of the fluorescent tube is d = 3 cm

the incoming negative charge in the tube is -e = 3 x 10¹⁸ electrons/second

the outgoing positive charge equals +e = 0.75 x 10¹⁸ electrons/ second

The current within the fluorescent tube results from both positive and negative charges which contribute to maintaining electrical neutrality in the conductor (fluorescent tube).

Q = It

I = Q/t

where;

I signifies current in Amperes (A)

Q represents charge measured in Coulombs (C)

t denotes time which is in seconds (s)

1 electron (e) accounts for 1.602 x 10⁻¹⁹ C

Thus, 3 x 10¹⁸ e/s can be computed as

= (3 x 10¹⁸ e/s  x 1.602 x 10⁻¹⁹ C) / 1e

= 0.4806 C/s

This reflects the negative charge per second (Q/t) = 0.4806 C/s

Meanwhile, the positive charge per second amounts to

(0.75 x 10¹⁸ e/s  x 1.602 x 10⁻¹⁹ C) / 1e

Thus, the positive charge per second is equal to 0.12015 C/s

The total charge per second in the tube is then obtained by summing both charges: Q / t = (0.4806 C/s + 0.12015 C/s)

                                                                I = 0.601 A

Therefore, the current within the tube computes to 0.601 A

The formula used is known as the Law of Universal Gravitation. The gravitational constant G is 6.67×10⁻¹¹ Nm²/kg². The Earth's mass is <span>5.972 ×10</span>²⁴ kg. The mass of the rocket is negligible in comparison to Earth’s mass, hence it is unnecessary for our calculations. Plugging in the values:

F = (6.67×10⁻¹¹ Nm²/kg²)(5.972 ×10²⁴ kg)/(4000 miles*(1.609 km/1 mile))²
F = 9616423.08 N

The work done is given by
W = Fd
W = (9616423.08 N)(2000 miles*1.609 km/mile)
W = 9.095×10¹⁰ Joules

Answer:

a) La velocidad promedio del récord de la carrera es de 35.2 km/h

b) El tiempo que tomará cubrir la primera mitad es 2h 42 min.

Explicación:

a) Para calcular la velocidad promedio del récord, se divide la distancia total por el tiempo:

v = distancia / tiempo

Ahora, expresaremos el tiempo en horas:

si 60 s es 1 min, entonces 37 s será (37 s · 1 min/60 s) 0.62 min.

Si 60 min es 1 h, entonces 40.62 min será (40.62 min · 1 h/60 min) 0.68 h.

Por lo tanto, el tiempo récord es 5.68 h.

La velocidad promedio será:

v = 2.00 × 10² km / 5.68 h = 35.2 km/h

b) Ahora que tenemos la velocidad y la distancia, podemos determinar el tiempo que le tomará al patinador cubrir esa distancia:

La velocidad será:

v = 1.05v = 1.05 · 35.2 km/h = 37.0 km/h

La distancia será:

2.00 × 10² km / 2 = 1.00 × 10² km

Luego:

v = distancia / tiempo

tiempo = distancia / v = 1.00 × 10² km / 37.0 km/h = 2.70 h

Si 1 h son 60 min, 0.70 h será (0.70 h · 60 min/h) 42 min.

Entonces, el tiempo necesario para cubrir la primera mitad es de 2h 42 min.