A person drives 70 km/h in 1 hour to the east, then 80 km/h for another hour to the east. What

Cosmic inflation refers to ____(A) the current period of cosmic acceleration.(B) stellar winds creating bubbles of gas.(C) the U

Brilliant_brown [7]

Answer:

(D) a brief early period of hyper rapid expansion of space-time.

Explanation:

Cosmic inflation is a theory which states that in an interval of 10⁻³⁶ seconds to around 10⁻³³ seconds after the big bang there was a massive expansion.

According to the big bang theory the universe came to be from a singularity i.e., a point of infinite gravitational field. The universe is expanding this means that according to the conservation of energy the universe was expanding from the beginning.

8 0

3 years ago

What does it mean if the moon is waxing and waning

konstantin123 [22]

Both verbs come from Olde English.
That's why everybody clearly understood their meaning until
a hundred years ago, but nobody understands them now.

"Waxing" = growing

For two weeks after the New Moon, it's growing toward Full.
First it's a waxing crescent for a week, then it's waxing gibbous.

"Waning" = shrinking

For two weeks after the Full Moon, it's shrinking toward New.
First it's waning gibbous for a week, then it's a waning crescent.

6 0

2 years ago

The voltage across the terminals of a 250nF capacitor is푣푣=�50푉푉, 푡푡≤0(푚푚1푒푒−4000푡푡+푚푚2푡푡푒푒−4000푡푡)푉푉, 푡푡 ≥0The initial current

olga2289 [7]

The first part of the question is not complete and it is;

The voltage across the terminals of a 250 nF capacitor is 50 V, A1e^(-4000t) + (A2)te^(-4000t) V, t0, What is the initial energy stored in the capacitor? Express your answer to three significant figures and include the appropriate units. t

Answer:

A) initial energy = 0.3125 mJ

B) A1 = 50 and A2 = 1,800,000

C) Capacitor Current is given by the expression;

I = e^(-4000t)[0.95 - 1800t]

Explanation:

A) In capacitors, Energy stored is given as;

U = (1/2)Cv²

Where C is capacitance and v is voltage.

So initial kinetic energy;

U(0) = (1/2)C(vo)²

From the question, C = 250 nF and v = 50V

So, U(0) = (1/2)(250 x 10^(-9))(50²) = 0.3125 x 10^(-3)J = 0.3125 mJ

B) from the question, we know that;

A1e^(-4000t) + (A2)te^(-4000t)

So, v(0) = A1e^(0) + A2(0)e^(0)

v(0) = 50

Thus;

50 = A1

Now for A2; let's differentiate the equation A1e^(-4000t) + (A2)te^(-4000t) ;

And so;

dv/dt = -4000A1e^(-4000t) + A2[e^(-4000t) - 4000e^(-4000t)

Simplifying this, we obtain;

dv/dt = e^(-4000t)[-4000A1 + A2 - 4000A2]

Current (I) = C(dv/dt)

I = (250 x 10^(-9))e^(-4000t)[-4000A1 + A2 - 4000tA2]

Thus, Initial current (Io) is;

Io = (250 x 10^(-9))[e^(0)[-4000A1 + A2]]

We know that Io = 400mA from the question or 0.4 A

Thus;

0.4 = (250 x 10^(-9))[-4000A1 + A2]

0.4 = 0.001A1 - (250 x 10^(-9)A2)

Substituting the value of A1 = 50V;

0.4 = 0.001(50) - (250 x 10^(-9)A2)

0.4 = 0.05 - (250 x 10^(-9)A2)

Thus, making A2 the subject, we obtain;

(0.4 + 0.05)/(250 x 10^(-9))= A2

A2 = 1,800,000

C) We have derived that ;

I = (250 x 10^(-9))e^(-4000t)[-4000A1 + A2 - 4000tA2]

So putting values of A1 = 50 and A2 = 1,800,000 we obtain;

I = (250 x 10^(-9))e^(-4000t)[(-4000 x 50) + 1,800,000 - 4000(1,800,000)t]

I = e^(-4000t)[0.05 + 0.45 - 1800t]

I = e^(-4000t)[0.95 - 1800t]

5 0

3 years ago

1. Which type of wire would be a better conductor of an electrical current?

Lelechka [254]

Answer:

1. a

2. b

3. b

Explanation:

1.

Resistance is the property of a conductor to offer resistance to the flow of current. The lower the resistance better is the conductivity of wire.

We know that the resistance of a wire depends on several factor which are inter-connected by an equation as:

$R=\rho.\frac{l}{a}$

where:

R = resistance of the wire

$l =$ length of the wire

$a=$ cross sectional area of the wire

from the above relation we observe that

$R\propto l$

$R\propto \frac{1}{a}$

Also when the temperature of the wire is significantly high then the lattice vibration cause obstruction in the path of the flowing charges and reduce the current flow.

2.

As the collision between the electrons and protons increases the speed of the flow of charges will decrease because the opposite charges attract each other and as we know that electrical current is the rate of flow of charge.

3.

Heating up of wire due to sunlight will cause lattice vibration in the conductor and will obstruct the movement of the charges which build up electric current, hence increasing the resistance of conductivity.

7 0

2 years ago

The component of acceleration perpendicular to an object’s velocity tells us: A. How the object’s speed changes. B. The influenc

vesna_86 [32]

Answer:

Option C is correct.

The component of acceleration perpendicular to an object’s velocity tells us How the object’s direction changes.

Explanation:

This acceleration is called radial/tangential acceleration. It is the reason why a body moving in circular motion with constant velocity can be said to also be accelerating because its direction is continuously changing. The acceleration is usually directed towards the centre of the circular motion of the body or trying to throw the body off its circular motion path.

5 0

3 years ago