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2 years ago

How much does it cost to operate a 25-w soldering iron for 8.0 hours if energy costs 8.0¢/kwh?

1 answer:

6 0

The power P is defined as the energy E per unit of time t:
$P= \frac{E}{t}$
In our problem, the power is P=25 W and the total time is t=8.0h, so we can calculate the total energy used during this time:
$E=Pt=(25 W)(8.0 h)=200 Wh=0.2 kWh$
The energy costs 8€ per each kwh, so we can write the following proportion:
$8€: 1kwh = x:0.2 kWh$
where x is the price corresponding to 0.2 kWh. Solving the proportion we find x:
$x= \frac{(8€)(0.2 kWh)}{1kWh}=1.6$ €

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Charge q1 is distance r from a positive point charge q. charge q2=q1/3 is distance 2r from q. what is the ratio u1/u2 of their p

makvit [3.9K]

We need the power law for the change in potential energy (due to the Coulomb force) in bringing a charge q from infinity to distance r from charge Q. We are only interested in the ratio U₁/U₂, so I'm not going to bother with constants (like the permittivity of space).

The potential energy of charge q is proportional to 
∫[s=r to ∞] qQs⁻²ds = -qQs⁻¹|[s=r to ∞] = qQr⁻¹, 

so if r₂ = 3r₁ and q₂ = q₁/4, then 
U₁/U₂ = q₁Qr₂/(r₁q₂Q) = (q₁/q₂)(r₂/r₁) 
= 4•3 = 12.

5 0

2 years ago

The dial of a scale looks like this: 00.0kg. A physicist placed a spring on it. The dial read 00.6kg. He then placed a metal cha

saveliy_v [14]

Answer:

d. The scale's resolution is too low to read the change in mass

Explanation:

If we want to find the change in energy of the spring, we will have to use the Hooke's Law. Hooke's Law states that:

F = kx

since,

w = Fd

dw = Fdx

integrating and using value of F, we get:

ΔE = (0.5)kx²

where,

ΔE = Energy added to spring

k = spring constant

x = displacement

The spring constant is typically in range of 4900 to 29400 N/m.

So if we take the extreme case of 29400 N/m and lets say we assume an unusually, extreme case of 1 m compression, we get the value of energy added to be:

ΔE = (0.5)(29400 N/m)(1 m)²

ΔE = 1.47 x 10⁴ J

Now, if we convert this energy to mass from Einstein's equation, we get:

ΔE = Δmc²

Δm = ΔE/c²

Δm = (1.47 x 10⁴ J)/(3 x 10⁸ m/s)²

Δm = 4.9 x 10⁻¹³ kg

As, you can see from the answer that even for the most extreme cases the value of mass associated with the additional energy is of very low magnitude.

Since, the scale only gives the mass value upto 1 decimal place.

Thus, it can not determine such a small change. So, the correct option is:

d. The scale's resolution is too low to read the change in mass

8 0

2 years ago

6. Starting from 1.5 miles away, a car drives toward a speed checkpoint and then passes it. The car travels at a constant rate o

loris [4]

For the answer to the question above,

To be 0.1 miles away from the check point ,
the car has to travel 1.4 miles OR 1.6 miles. 

53 miles = 60 minutes

1.4 miles = 1.4 / 53 X 60 = 1.5849056 minutes OR 95.1 seconds

1.6 miles = 1.6 /53 X 60 = 1.8113207 minutes OR 108.7 seconds
So the answer is 95.1s and 108.7s
I hope my answer helped you

7 0

2 years ago

Explain the process of ionic bond formation between K( potassium a metal) and Br(bromine a nonmetal)

SVETLANKA909090 [29]

Potassium belongs to group IA of the elements. This means that it will give up one of its electrons to form the cation K+. Opposite to that is bromine in which it accepts one electrons to form the anion Br-. The binding of these elements will form KBr and is formed from transfer of electron from one element to the other. This is the mechanism of ionic bond formation.

8 0

2 years ago

Read 2 more answers

Classify the sentences based on whether they describe temperature or thermal energy.

KiRa [710]

Thermal energy energy that has hot cold or warm
Temp.Energy is the out come of the thermal engery and affects Earth and space

7 0

2 years ago