a light bulb is 4.1 m from a surface. how much luminous flux must the bulb produce if the illuminance required is 22 lx?

(a) Aircraft sometimes acquire small static charges. Suppose a supersonic jet has a 0.500 - μC charge and flies due west at a sp

12345 [234]

(a) $2.64\cdot 10^{-8} N$ north

We can treat the aircraft as a single point charge moving in a magnetic field. In this case, the magnetic force exerted on the plane is

$F=qvB sin \theta$

where

$q=0.500 \mu C = 0.500\cdot 10^{-6} C$ is the charge on the plane

v = 660 m/s is the velocity

$B=8.00\cdot 10^{-5} T$ is the magnitude of the magnetic field

$\theta=90^{\circ}$ is the angle between the direction of motion of the jet and of the magnetic field

Substituting,

$F=(0.5\cdot 10^{-6})(660)(8.0\cdot 10^{-5})=2.64\cdot 10^{-8} N$

The direction can be found by using Fleming's left hand rule. We have:

- index finger: magnetic field direction (straight up)

- middle finger: velocity of the plane (due west)

- force: thumb --> north

(b) Not negligible

As we can see from part (a), the magnitude of the force is not really big, so the effects are negligible.

For instance, we can compare this force with the weight of a plane. If we take a Boeing 737, its mass is about 80,000 kg, so its weight is

$W=mg=(80000)(9.8)=784,000 N$

As we can see, this is several orders of magnitude bigger than the magnetic force calculated at point (a), so the effects of the magnetic force are negligible.

8 0

2 years ago

A particular material has an index of refraction of 1.25. What percent of the speed of light in a vacuum is the speed of light i

beks73 [17]

Answer:

80% (Eighty percent)

Explanation:

The material has a refractive index (n) of 1.25

Speed of light in a vacuum (c) is 2.99792458 x 10⁸ m/s

We can find the speed of light in the material (v) using the relationship

n = c/v, similarly

v = c/n

therefore v = 2.99792458 x 10⁸ m/s ÷ (1.25) = 239 833 966 m/s

v = 239 833 966 m/s

Therefore the percentage of the speed of light in a vacuum that is the speed of light in the material can be calculated as

(v/c) × 100 = (1/n) × 100 = (1/1.25) × 100 = 0.8 × 100 = 80%

Therefore speed of light in the material (v) is eighty percent of the speed of light in the vacuum (c)

3 0

2 years ago

Read 2 more answers

The two major problems with most motor vehicles are that they burn fossil fuels and _____________.

Citrus2011 [14]

Answer:

A. Create radioactive waste i believe

Explanation:

8 0

2 years ago

Read 2 more answers

Two negative charges that are both -0.3C push each other apart with a force of 19.2 N. How far apart are the two charges?

Paha777 [63]

<span>Using Coulomb's law: k*(-0.3)*(-0.3)/(d^2)=19.2 D is the distance between the two negative charges</span>

8 0

2 years ago

A pulley 12 cm in diameter is free to rotate about a horizontal axle. A 220-g mass and a 470-g mass are tied to either end of a

Aleks [24]

Answer:0.147 N-m

Explanation:

Given

Diameter of Pulley $d=12 cm$

radius $r=6 cm$

mass of first object $m_1=220 gm$

mass of second object $m_2=470 gm$

Now both masses will exert a torque a on Pulley

Torque due to first Pulley $T_1=m_1g\cdot r$

$T_1=0.22\times 9.8\times 0.06=0.129 N-m$

Torque due to second mass on Pulley $T_2=m_2g\cdot r$

$T_2=0.276 N-m$

Total Torque by masses $T_{net}=T_2-T_1$

$T_{net}=0.276-0.129=0.147 N-m$

so we need to apply a torque of magnitude 0.147 N-m opposite to the direction of $T_{net}$

3 0

2 years ago