Calculate the efficiency of the following appliances:
1. A radiator that converts 1000) of electrical energy into 900J
of heat energy and 100J of light energy
2. A torch that converts 100J of chemical energy into 35) of
light energy and 65J of heat energy
3. A car that converts 10,000J of chemical energy into 6000) of
kinetic energy and 4000J of heat energy.
4. An energy saver light converts 1,000J of electrical energy
into 7003 of light energy and 300J of heat energy.
5. A speaker converts 100J of electrical energy into 50J of
sound energy and 50J of heat and kinetic energy.
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Doppler frequency, the other car hear before they pass each other is 668.68 Hz.

Frequency is the number of occurrences of a repeating event per unit of time.

The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to the wave source.

According to the Doppler Effect, the frequency observed is

  [tex]fo=fs\frac{v+v_{o} }{v-v_{s} }[/tex]

[tex]f_{o}=595\frac{343+20 }{343-20 }\\f_{o} = 668.68 Hz[/tex]

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Answer:

Elements in the same group have the same number of valence electrons.

When moving right across a period, the valence electrons of the main group elements increase by one.

When moving down a group, the valence electrons of the main group elements increase by one.

Elements in the same period have the same number of valence electrons.

Elements in the same period of the periodic table have valence electrons in the same energy levels.

When elements are in the same period on the periodic table, it means that they have the same number of shells.

The energy level of valence electrons in a atom depends on how far it is from the nucleus. This means that:

For instance, Boron, Carbon and Nitrogen will have valence electrons in the same energy levels.

In conclusion, elements in the same period will have valence electrons in the same energy levels.

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Answer:

But negative acceleration means that the rate of change of velocity is negative or velocity decreases. Example: (1) When we apply brakes in a moving car, then negative acceleration acts on it and the car stops. (2) When we throw a ball upwards, then also negative acceleration acts on it.

Explanation:

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MATHEMATICALLY A NEGATIVE ACCELERATION MEANS YOU WILL SUBTRACT FROM THE CURRENT VALUE OF THE VELOCITY.

We know

[tex]\boxed{\sf Spring\:constant(K)=\dfrac{F}{x}}[/tex]

[tex]\\ \sf\longmapsto K=\dfrac{1}{0.5}[/tex]

[tex]\\ \sf\longmapsto K=2N/m[/tex]

Explanation:

string roller is called an example of wheel and axel because The thin rod which needs to be turned is called the axle and the wider object fixed to the axle, on which we apply force is called the wheel.

hence the we apply force on the roller and the string gets tight.

The magnitude (size or numerical value) and the direction.

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Answer with Explanation:

Let me answer this in a simple way, since the density of stone is greater than that of water, the stone sinks as the weight of the stone is greater than the weight of water displaced by it. But the ship is designed in such a way that the relative density of the ship always becomes less than that of water. Therefore, the weight of the water displaced becomes equal to the total weight of the ship and thus it floats.

There are many other ways to explain this but this should give you the general idea.

Answer:

Explanation:

We first need to convert the 40 km/h to m/s. Going by the fact that 40 has only 1 significant figure in it, 40 km/h = 10 m/s. The rest of the values are in their proper labels. We will use the equation:

[tex]v^2=v_0^2+2a[/tex]Δx where the final velocity is 0 because the car is coming to a stop at the end; the initial velocity is 10 m/s, the acceleration (or, rather, deceleration) is -.5 m/s/s, and our unknown which is displacement. Filling in:

[tex]0=(10)^2+2(-.5)[/tex]Δx and solving for Δx:

Δx = [tex]\frac{-100}{2(-.5)}[/tex] which ends up being simply that

Δx = 100 m

Answer:

hi

Explanation:

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Answer:

The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current. The relationship between resistance and the area of the cross section of a wire is inversely proportional .

The best way to think about this is:

A thick/wide road, with many lanes, can carry more cars than a thin/narrow road, with only one or two lanes.

Answer:

Explanation:

There is no pressure of your feet on the scales, and no pressure of the floor on the scales, so the scales will read zero*. Hence, your weight, in a freely falling lift is zero

Answer:

96 meters

Explanation:

d = st

d = (8 m/s)(12 s)

d = 96 m

Answer:

Explanation:

By being close to an atom that will gladly take the electrons being offered.

Suppose you are talking about Be. It is in the second column. It has two outer electrons that can be given away. It will not give away one of the two remaining electrons because they are too close to the + nucleus.

Along comes a Fluorine atom. It has 7 electrons in its outer ring. The chemistry of the situation allows it to take on one of the two electrons Be is offering. It is all a matter of charges and attractions.

Another Fluorine atom will take on the remaining electron from the Be. The outer ring cannot take on more than 1 electron, but that is enough

Answer:

False -> negative charge

Answer:

false

Explanation: electrons are negative charges

protons are positive charges

Radiation is energy that comes from a source and travels through space at the speed of light. This energy has an electric field and a magnetic field associated with it, and has wave-like properties. You could also call radiation “electromagnetic waves”.

cdc

Explanation:

p = F /A

F = P×A

F = 30,000 Pa / 0.1 m²

F = 300,000 N

Answer:

Wait until the end of the semester to complete all work.

Explanation:

this is the obvious answer.

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Answer:

Wait until the end of the semester to complete all work

Answer:

False.

Explanation:

A warm up is stretching in the beginning.

Option ( iv ) is the correct answer.

A vector quantity the physical quantity that has both direction as well as magnitude.

Answer:

1) The kinetic energy of the object after it drops for 2.0 seconds is approximately 384.9 Joules

2) The potential energy of the object after it drops for 2.0 seconds is approximately 204 J

Explanation:

1) The given mass of the object, m = 2.0 kg

The height from which the object is dropped, h = 30 m

The kinetic energy of the object after it drops for 2.0 seconds = Required

Kinetic energy, K.E. = (1/2)·m·v²

Where;

v = The velocity of the object

The kinematic equation for finding the velocity of the object is presented as follows;

v = u + g·t

Where;

u = The initial velocity of the object = 0

g = The acceleration due to gravity of the object ≈ 9.81 m/s²

t = The time of motion of the object = 2.0 seconds

∴ The velocity after 2 seconds, v ≈ 0 + 9.81 m/s² × 2 s = 19.62 m/s

The kinetic energy, K.E. after 2 seconds as the object drops is given as follows;

[tex]K.E._{(after \ two \ seconds)}[/tex] = (1/2) × 2.0 kg × (19.62 m/s)² = 384.9444 J ≈ 384.9 J

2) The total energy, M.E. of the object at the top, h = 30 m, u = 0, is given as follows;

The total mechanical energy, M.E. = P.E. + K.E.

M.E. = m·g·h + (1/2)·m·u²

∴ M.E. = 2.0 kg × 9.81 m/s² × 30 m + 0 = 588.6 J

M.E. = 588.6 J

Given that the total mechanical energy, M.E., is constant, we have;

At 2.0 seconds, M.E. = 588.6 J , K.E. ≈ 384.9 J, P.E. = M.E. - K.E.

∴ P.E. = 588.9 J - 384.9 J ≈ 204 J

The potential energy after it drops 2.0 seconds, P.E. ≈ 204 J

[tex]\boxed{\sf W=Fscos\Theta}[/tex]

[tex]\\ \sf\longmapsto W=150(50)cos 60[/tex]

[tex]\\ \sf\longmapsto W=7500\times \dfrac{1}{2}[/tex]

[tex]\\ \sf\longmapsto W=3750J[/tex]

Answer:

0.80 m

Explanation:

Neglecting friction, the total mechanical energy of the pendulum is constant.

E = K + U where K = kinetic energy and U = potential energy.

At its release point of 0.80 m, the pendulum bob has a mechanical energy which is equal to its potential energy, since, its initial kinetic energy is zero. By the time the bob swings to the other end, it has a mechanical energy equal to it initial potential energy since total energy is conserved.

Neglecting friction, the pendulum bob would swing back to its original height of 0.80 m since the total mechanical energy is conserved and at its highest point, it is purely potential energy.

So, the height the pendulum bob swings to after release from a height of 0.80 m neglecting fiction is 0.80 m.

Answer:

w = 0.01 t⁻²   rad/h

Explanation:

Let's use trigonometry to find the elevation angle of the telescope, we assume that the rocket remains fixed in the telescope.

        tan θ = CO / CA

the adjacent leg is CA = 16 km = 16 10³ m

Let's use kinematics to find the height of the rocket

          v = y / t

          y = v t

this height is equal to the opposite leg

          CO = v t

we substitute

         tan θ = vt / 16

         tan θ = 1200/16 t

         tan θ = 75 t

         θ = tan⁻¹ ( 75 t )

speed is defined by

          w = dθ/dt

          w = [tex]\frac{1}{1 + (75 t)^2} \ 75[/tex]  

as time increases we can neglect the 1 of the denominator

          w = 1/75 t²

          w = 0.0133 t⁻²

Using three significant figures

           w = 0.01 t⁻²   rad/h

for this answer the time must be given in hours

Answer:

Pascal is a derived unit because it cannot be expressed in any physics terms, but it is an expression of fundamental quantities.

Explanation:

[tex]{ \sf{Pasacal \: ( Pa) = \frac{newtons}{metres {}^{2} } }} \\ \\ { \sf{Pasacal \: (Pa) = \frac{kg \times {ms}^{ - 2} }{ {m}^{2} } }}[/tex]

my views

Explanation:

Figure (8) shows a rod made up of copper and wood joined together. The rod is heated at the joint in the centre for about a minute. At which point – A, B, C or D, would it show the lowest temperature? PLEASE GIVE REASONS ALSO(MINIMUM 2)

Answer:

The average velocity of an object is its total displacement divided by the total time taken. In other words, it is the rate at which an object changes its position from one place to another.

Explanation:

Average velocity is a vector quantity. The SI unit is meters per second. However, any distance unit per any time unit can be used when necessary, such as miles per hour (mph) or kilometer per hour (kmph)

Answer:

the ratio of total displacement by total time taken

Answer:

cần cung cấp 70 độ vì nước sôi ở 100°C

Explanation:

Answer:

0.25p.a

Explanation:

force=15N area=60m²

so pressure =force/area =15N/60m²=0.25p.a