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3 years ago

Which two energy sources together provide more than 50% of the energy needs of the United States?

Physics

1 answer:

SVEN [57.7K]3 years ago

6 0

Answer:

Petroleum ( over 30% energy )

Natural gas ( over 30% energy )

Explanation:

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The radar system of a navy cruiser transmits at a wavelength of 1.4 cm, from a circular antenna with a diameter of 2.7 m. At a r

Goshia [24]

Answer:

Distance will be 49.34 m

Explanation:

We have given wavelength $\lambda =1.4cm =0.014m$

Diameter of the antenna d = 2.7 m

Range L = 7.8 km = 7800 m

We have to find the smallest distance hat two speedboats can be from each other and still be resolved as two separate objects D

We know that distance is given by $D=\frac{L1.22\lambda }{d}=\frac{7800\times 1.22\times 0.014}{2.7}=49.3422m$

So distance D will be 49.34 m

4 0

3 years ago

A crate lies on a plane tilted at an angle θ = 22.5 ∘ to the horizontal, with μk = 0.19.

ValentinkaMS [17]

A) $2.03 m/s^2$

Let's start by writing the equation of the forces along the directions parallel and perpendicular to the incline:

Parallel:

$mg sin \theta - \mu_k R = ma$ (1)

where

m is the mass

g = 9.8 m/s^2 the acceleration of gravity

$\theta=22.5^{\circ}$

$\mu_k = 0.19$ is the coefficient of friction

R is the normal reaction

a is the acceleration

Perpendicular:

$R-mg cos \theta =0$ (2)

From (2) we find

$R=mg cos \theta$

And substituting into (1)

$mg sin \theta - \mu_k mg cos \theta = ma$

Solving for a,

$a=g sin \theta - \mu_k g cos \theta = (9.8)(sin 22.5)-(0.19)(9.8)(cos 22.5)=2.03 m/s^2$

B) 5.94 m/s

We can solve this part by using the suvat equation

$v^2-u^2=2as$

where

v is the final velocity

u is the initial velocity

a is the acceleration

s is the displacement

Here we have

v = ?

u = 0 (it starts from rest)

$a=2.03 m/s^2$

s = 8.70 m

Solving for v,

$v=\sqrt{u^2+2as}=\sqrt{0+2(2.03)(8.70)}=5.94 m/s$

6 0

3 years ago

If in 30 mins Alex runs to a store that is 4 km away, what is her average speed in km/h

masha68 [24]

15 km 30 divided by 4 is 7.5 km in 30 min times that by 2 the answer is 15

6 0

3 years ago

Why are the plates in a capacitor parallel to each other?

TiliK225 [7]

To have a uniform field. The field is the voltage between the plates divided by the distance between the plates. If the distance varies so would the field between them.

6 0

4 years ago

Read 2 more answers

If a wave has a speed of 12 m/s and a frequency of 4hz what is its wavelength

ELEN [110]

Apply:
wavelength = speed of wave / frequency
wavelength = 12 m/s / 4 Hz = 48 m

6 0

3 years ago