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3 years ago

Which best explains what happens to the motion of the pendulum?

Physics

2 answers:

Komok [63]3 years ago

7 0

The answer is A, I just learned about this a few days ago!

inessss [21]3 years ago

7 0

I think the answer is A

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When an RL circuit is connected to a battery, which is true about its initial and final states?

zubka84 [21]

Answer:A

Explanation:

In R-L circuit current is given by

$i=i_0\left [ 1-e^{\frac{-t}{L/R}}\right ]$

where i=current at any time t

$i_0=maximum\ current$

R=resistance

L=Inductance

at t=0 $e^{\frac{-t}{L/R}}$ approaches to 1

therefore $i=i_0\left [ 1-1\right ]$

i=0

when t approaches to $\infty$ , $e^{\frac{-t}{L/R}}$ approaches to zero

thus $i=i_0$

thus we can say that initially circuit act as broken wire with zero current

and it increases exponentially with time and act as ordinary connecting wire

7 0

4 years ago

A machine does 500 j of work in 20 sec. What is the power of this machine?

NNADVOKAT [17]

Explanation:

P=W/t

P=500/20

P=25 W

6 0

3 years ago

Physics question 28 plz help me

Alexus [3.1K]

Answer:

a. I = 30 A

b. E = 1080000 J = 1080 KJ

c. ΔT = 12.86°C

d. Cost = $ 4.32

Explanation:

The current in the coil is given by Ohm's Law:

$V = IR\\I = \frac{V}{R}$

where,

I = current = ?

V = Voltage = 120 V

R = Resistance = 4 Ω

Therefore,

$I = \frac{120\ V}{4 \Omega}\\$

I = 30 A

The energy can be calculated as:

$E = VIt\\E = (120\ V)(30\ A)(5\ min)(\frac{60\ s}{1\ min})\\$

E = 1080000 J = 1080 KJ

For the increase in the temperature of water:

$E = mC\Delta T\\$

where,

m = mass of water = 20 kg

C = specific heat of water = 4.2 KJ/kg.°C

Therefore,

$1080\ KJ = (20\ kg)(4.2\ KJ/kg.^oC)\Delta T$

ΔT = 12.86°C

First, we will calculate the total energy consumed:

$E=(Power)(Time)\\E=VI(Time)\\E = (120\ V)(30\ A)(0.5\ h/d)(30\ d)\\E = 54000\ Wh\\E = 54 KWh$

Now, for the cost:

$Cost = (Unit\ Cost)(Energy)\\Cost = (\$ 0.08\KWh)(54\ KWh)$

Cost = $ 4.32

7 0

3 years ago

You're driving down the highway late one night at 21 m/s when a deer steps onto the road 35 m in front of you. Your reaction tim

andreev551 [17]

Speed with which initially car is moving is 21 m/s

Reaction time = 0.50 s

distance traveled in the reaction time d = v t

d = 21 * 0.50 = 10.5 m

deceleration after this time = -10 m/s^2

now the distance traveled by the car after applying bakes

$v_f^2 - v_i^2 = 2a d$

$0 - 21^2 = 2(-10)d$

$d = 22.05 m$

so total distance moved before it stop

d = 22.05 + 10.5 = 32.55 m

so the distance from deer is 35 - 32.55 = 2.45 m

now to find the maximum speed with we can move we will assume that we will just touch the deer when we stop

so our distance after brakes are applied is d = 35 - 10.5 = 24.5 m

again by kinematics

$v_f^2 - v_i^2 = 2 ad$

$0 - v^2 = 2(-10)(24.5)$

$v = 22.1 m/s$

so maximum speed would be 22.1 m/s

5 0

3 years ago

An amount of energy is added to ice, raising its temperature from -10Â°C to -5Â°C. A larger amount of energy is added to the sam

lara [203]

Answer:

The correct option is;

B) The specific heat of ice is less than that of water.

Explanation:

Here we have

Let the amount of energy added to the ice at -10 C to raise the temperature to -5 C be X J

Let the amount of energy added to the water at 15 C to raise the temperature to 20 C be Y J

We know that the heat required, ΔQ to raise the temperature of a substance is given by

ΔQ = m·c·Δθ

Where:

m = Mass of the substance

c = Specific heat capacity

Δθ = Temperature change

Since the mass of the ice and the water are the same, so also is the change in temperature, (-5 - (-10) = 5 and 20 - 15 = 5) we have

for m₂·c₂·Δθ₂ > m₁·c₁·Δθ₁

Where:

m₁, c₁, Δθ₁, is for the ice and m₂, c₂, Δθ₂ is for the water and

m₁ = m₂

Δθ₁ = Δθ₂

Therefore,

c₂ > c₁ = c₁ < c₂

That is the specific heat capacity of the ice is lesser than the specific heat capacity of the water.

4 0

3 years ago

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