what happens when a force is applied to an object while the object moves in a direction opposite to the force?

a. negative work is done
b. work is done only if the force causes a decrease in speed
c. positive work is done
d. work is done only if the force causes an increase in speed.

Answer:

Kinetic energy is referred to the energy associated with movement and or motion, thus the only object that is moving would be A boat sailing across the ocean.

Explanation:

All elements in the same group have the same number of electrons in the outermost energy level. Option C is correct.

The periodic table is an organization of all known elements in order of increasing atomic number and repeating chemical characteristics.

They are organized in a tabular format, with a row representing an era and a column representing a group. E elements are ordered in increasing atomic number order from left to right and top to bottom.

Thus, Elements of the same group will have the same valence electron configuration and, as a result, will have comparable chemical characteristics.

Each set of elements has an equal amount of electrons in the outer orbital. Valence electrons are another name for the outer electrons.

They are the electrons interacting with other elements in chemical bonding. Each element in group one, the first column, has one electron in its outer shell.

Hence option C is correct.

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The correct statement about the sun and the earth is that only about half of the suns energy hits the earths surface.

The sun is the source through which energy reaches the earth. The sun is a large star that produces energy by the process of nuclear fusion.

Hence, the correct statement about the sun and the earth is that only about half of the suns energy hits the earths surface.

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Explanation:

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Answer:

D

Explanation:

Mass is the amount of matter your body has ....does not change on the Moon.

there is less gravity .....so your WEIGHT would decrease

Answer:

a

Explanation:

Explanation:

an object's gravitational potential energy Eg is m×g×h where:

m=mass

g=9.8m/s²

h=height relative to the closest object below it (because it cannot potentially fall through it

so Eg = 15×9.8×5=735J

Answer:

( 688.29 , 276.66 )   meters

Explanation:

Break into horizontal and vertical components

x = 100 cos 55  = 57.36 m/s      

   the x coordinate is then 12 seconds * 57.36 m/s = 688.29 meters

y coordinate is a bit more complex because of the curved path due to gravity

Original y velocity =  100 sin 55

y = vo t - 1/2 (9.81)(t^2)

y =  100 sin 55  (12)  - 1/2 (9.81) (12)^2

      yf = 276.66   meters

Answer:

2.5 grams

Explanation:

p = mv

m = p/v

m = 0.0332 / 13.3

m = 0.0025kg

0.0025 x 1000 = 2.5

m = 2.5g

Answer:

My explanation and answer are down here↓:

Explanation:

p→q is false only when p is true and q is false.

∴p→(q∨r) is false when p is true and (q∨r) is false, and

q∨r false when both q,r are false.

Hence T,F,F.

Answer:

Explanation:

Solution

In physics, a period is a measurement of time. The answer must be either B or C. It is a direct measurement of time, not its reciprocal. So the answer is B. A and D is a measurement of the actual cycle that it takes before the motion begins to repeat itself.

Answer

B

Answer:

A

Explanation:

5.2mm/s

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Magnetic stripes provide evidence of seafloor spreading due to their occurrence in the region of sea floor.

When the Earth's magnetic field reverses, a new stripe starts to form. Such magnetic patterns enable the scientist to recognize the occurrence of sea-floor spreading and provides strongest evidence for the theory of plate tectonics.

So we can conclude that magnetic stripes provide evidence of seafloor spreading due to their occurrence in the region of sea floor.

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The activity of the contaminant will be 3.5 ×10⁻¹⁰ Bq if the contaminant is 1.1MeV Beta Emitter.

Disclaimer, here the m is taken as 0.5kg.

Given, REM = 1500

Time, t= 1 minute =60 seconds

For beta particles,

RBE (Relative Biological Effectiveness) =2.

Absorbed dose,  D =REM/RBE= 1500/2 = 750rad

As 100 rad=1 J/kg,

750 rad=7.5 J/kg

So, D=7.5 J/kg

D= total energy absorbed (E)/mass (m)

7.5 J/kg=E/m

E =7.5 ×0.5 = 3.75J

Therefore, the number of beta particles absorbed is 3.75 J.

The number of beta particles absorbed,

As 1 MeV= 1.6 ×10⁻¹³J

So, converting 1.1 MeV in J, 1.1×1.6 ×10⁻¹³J=1.76×10⁻¹³J

Numbers of beta particles,

n=3.75J/1.76×10⁻¹³J

n=2.13×10⁻¹²

Hence, the number of beta particles is 2.13×10⁻¹².

Activity, A= n/t

where n is the number of beta particles and t is the time.

A= n/t=(2.13×10⁻¹²)/60

A= 3.5 ×10⁻¹⁰ Bq

So, the activity is 3.5 ×10⁻¹⁰ Bq.

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The velocity of the third piece is 124.02 m/s at 1.05⁰ below the horizontal.

The velocity of the third piece is calculated from the principle of conservation of linear momentum.

mu = m₁u₁ + m₂u₂ + m₃u₃

where;

6(22)sin(0) = 2(10)sin32 - 1(8)sin(28) + 3u₃y

0 = 6.84 + 3u₃y

u₃y = -6.84/3

u₃y = -2.28 m/s

ΔP = Pf - Pi = J

where;

2640(0.1) = 2(10)cos32 +  1(8)cos(28) + 3u₃x - 6(22)

264 = -108 + 3u₃x

3u₃x = 372

u₃x = 372/3

u₃x = 124 m/s

u₃ = √(124² + 2.28²)

u₃ = 124.02 m/s

tanθ = u₃y/u₃x

tanθ = 2.28/124

tanθ = 0.018

θ = 1.05⁰ (below the horizontal)

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The height of the object will be -5.19 cm

A concave mirror's reflecting surface curves inward and away from the light source. Light is reflected inward to a single focus point via concave mirrors. Concave mirrors, in contrast to convex mirrors, produce a variety of images depending on the object's to the mirror.

Given an object 24.0 cm from a concave mirror creates a virtual image at -33.5 cm. if the image is 7.25 cm tall

So let,

v =  Image distance from the mirror = -33.5 cm

u = object distance from the mirror (concave) = 24 cm

hi = Image height = 7.25 cm

h = height of the object = ?

Using below formula to find height of the object

-v/u = hi/h

Putting all value in the formula we get

-(-33.5)/(-24) = 7.25/h

h = -5.19 cm

Therefore the height of the object will be -5.19 cm

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They use less wire, A

Wave 3 will have the highest frequency. Option c is correct.

What is the frequency?

Frequency is defined as the number of repititions of a wave occurring waves in 1 second.

Frequency is given by the formula as,

[tex]\rm v = \lambda \times f[/tex]

If the wavelength of the wave is content the velocity of the wave is directly propotional to the frequency.

The velocity of wave 3 is maximum. So that the wave 3 will have the highest frequency.

Hence option c is correct.

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Hence, the time required is approximately equal to 4 minutes and 39 seconds.

Given, Power, P = 300 W= 300J/s

Power= Energy per second

Mass, m= 0.25 kg

Initial Temperature= 20.0°C

Final Temperature= 100.0°C

Temperature difference, T =( 100-20)°C= 80.0°C

Specific heat of water, S= 4184 J/kg°C

Energy can be represented as

E=mST

where E is the energy, m is the mass, S is the specific heat of water and T is the temperature difference.

As Energy can be written as the product of time and power, E=Pt

Pt=mST

So,

t=(msT)/P

t=(0.25×4184×80)/300

Time, t = 278.934 seconds= 4 minutes and 39 seconds.

Hence, 4 minutes and 39 seconds will be required for a 300.0 W immersion heater to heat 0.25 kg of water from 20.0°C to 100.0°C.

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The speed of sound waves in air at room temperature T=20° is 344.035 m/s.

The range of wavelength in air to which the human ear (which can hear frequencies in the range of 20 – 20,000Hz) is sensitive is  17.20 m to  0.0172 m.

The wavelength is the distance between the adjacent crest or trough of the sinusoidal wave. The wavelength is the reciprocal of the frequency of the wave.

Wavelength λ = c/f

where c is the speed of sound wave.

Given the room temperature T = 20 +273 = 293K

The velocity of sound wave is given by

v = √(γRT/m)

​where γ =1.4 , m = 28.8×10⁻³ kg/mol  R = 8.31 J/K.mol

Substituting the values, we get

v = 344.035 m/s

Thus, the speed of sound wave is 344.035 m/s

​

The human ear can hear frequencies in the range of 20 – 20,000Hz.

The wavelength corresponding to 20Hz is

λ = c/f

λ =  344.035 /20

λ  = 17.20 m

The wavelength corresponding to 20,000Hz is

λ =  344.035 /20000

λ  = 0.0172 m

Thus, the range of wavelength is 17.20 m to  0.0172 m sensitive to human ear.

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Answer:

Following precautions for obtaining the refractive index of a triangular glass prism:-

Explanation:

(1) All the faces of the prism should be neat and clean.

(2) Pins for holding the paper on the drawing board must be pinned perpendicular to the paper for better handling.

(3) While fixing the pins for checking the refractive index of the prism, make sure that the reflective images of the pins should be aligned to your eye to avoid any type of parallax error.

(4) Pins should not be removed or pinned again during the experiment.

(5) Avoid mishandling of the prism.

(6) Same edge of the prism should be taken as vertex for observations.

(7) For drawing the boundary of the prism, a sharp pencil should be used.

(8) Soft board and pointed pins should be used.

(9) The distance between the pins should be 5 cm or more.

(10) Make sure the glass slab or prism taken are polished and not broken.

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Answer:

672 000 J      or 672 kJ

Explanation:

change in the thermal energy = mass x specific heat capacity x temperature change

     =   2 kg * 4200J/kg-C *80 C =672000 J

Answer:

D

Explanation:

GPE = mgh

GPE / gh = m

m = GPE/gh

m = 915 / 6.5 x 9.8

m = 915 / 63.7

m = 14.4kg

Answer:

a magnetic force

Explanation:

Answer:

Explanation:

Comment

I think the best answer is probably A.  It's not the best reason for Earth loosing it's helium, but it is the only one that is close. The Earth derives some of its Helium (most) by the decomposition process of radio active high weight chemical that break down. Helium combines with practically nothing so once it gets moving, very little will stop it. That's the way we loose our Helium.

Still answer A.

(a) Let [tex]v[/tex] be the maximum linear speed with which the ball can move in a circle without breaking the cord. Its centripetal/radial acceleration has magnitude

[tex]a_{\rm rad} = \dfrac{v^2}R[/tex]

where [tex]R[/tex] is the radius of the circle.

The tension in the cord is what makes the ball move in its plane. By Newton's second law, the maximum net force on it is

[tex]F = (1.500\,\mathrm{kg}) a_{\rm rad}[/tex]

so that

[tex](1.500\,\mathrm{kg}) \dfrac{v^2}{1.50\,\rm m} = 64.0\,\mathrm N[/tex]

Solve for [tex]v[/tex] :

[tex]v^2 = \dfrac{(64.0\,\mathrm N)(1.50\,\mathrm m)}{1.500\,\rm kg} \\\\ \implies \boxed{v = 8.00 \dfrac{\rm m}{\rm s}}[/tex]

(b) The net force equation in part (a) leads us to the relation

[tex]F = \dfrac{mv^2}R \implies v = \sqrt{\dfrac{FR}m}[/tex]

so that [tex]v[/tex] is directly proportional to the square root of [tex]R[/tex]. As the radius [tex]R[/tex] increases, the maximum linear speed [tex]v[/tex] will also increase, so the cord is less likely to break if we keep up the same speed.

Hello!

Begin by plugging in the values for m and n. We get the equation for the velocity of the particle to be:
[tex]v(t) = 10 + 2t^2[/tex]

A.

To find the change in velocity over the interval (2s ≤ t ≤ 5s), we can simply find the difference in the velocities at these times.

[tex]\Delta v= v_f - v_i[/tex]

For this situation:
[tex]\Delta v = v(5) - v(2)[/tex]

Substitute these times for 't' into the equation and solve.

[tex]v(5) = 10 + 2(5^2) = 60 \frac{cm}{s}\\\\v(2) = 10 + 2(2^2) = 18 \frac{cm}{s}\\\\\Delta v = 60 - 18 = \boxed{42 \frac{cm}{s}}[/tex]

B.

To find the average acceleration, we must take the SLOPE of the velocity function over this interval using the slope formula:

[tex]a_{avg} = \frac{v_f - v_i}{\Delta t}[/tex]

Plug in the values for the particle's velocity at t = 2 s and 5 s that we solved for above.

[tex]a_{avg} = \frac{60- 18}{5 - 2}\\\\a_{avg} = \frac{42}{3} = \boxed{ 14 \frac{cm}{s^2}}[/tex]

C.

The instantaneous acceleration can be found by taking the derivative of the v(t) function using the power rule. Recall:
[tex]\frac{dy}{dx} x^n = nx^{n-1}[/tex]

Using this rule:
[tex]a(t) = v'(t) = 2(2t) = 4t[/tex]

Substituting in t = 2 s:
[tex]a(2) = 4(2) = \boxed{8 \frac{cm}{s^2}}[/tex]

Answer:

108 is the correct answer

Answer:

r = 2.0m

when t = 0, the angular displacement is zero.

Explanation:

When the angular acceleration is 0.01 m/s2, you can calculate

angular acceleration = change in angular velocity/ time