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finlep [7]
3 years ago
12

A book is launched up along the rough incline. Kinetic energy given to a book at initial point is 100 J. Book comes to stop at s

ome point having potential energy 80 J, after what book starts to slide back. What will be its kinetic energy when it will return to the initial launching point?
(A) 60 J
(B) 100 J
(C) 80J
(D) 180 J
Physics
1 answer:
den301095 [7]3 years ago
7 0

Answer:

(A) 60 J

Explanation:

At state 1

KE₁=100 J

At state 2

KE₂ = 0

U₂=80 J

Given that surface is rough so friction force will act in opposite to the direction of motion

Lets take work done by friction = Wfr

From work power energy

Work done by all forces = Change in kinetic energy

Wfr + U₂=ΔKE

Wfr+80 = 100

Wfr= 20 J

Now when book slides from top position then

Wfr+ U = KEf - KEi

-20 + 80 = KEf-0

KEf= 60 J

(A) 60 J

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Two large, plastic tubs were filled with soil The soil was shaped to create a mound in each tub. The starting height of each mou
shutvik [7]

Answer:

b

Explanation:

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2 years ago
Why won't a very bright beam of red light impart more energy to an ejected electron than a feeble beam of violet light?
bearhunter [10]
This is related to the energy carried by photons of light the energy of each photon is proportional to the frequency of the light since red light has a lower frequency then violet light and photons of red light carry less energy than the photons of violet light as a result the red protons eject electrons that have less energy than the ejected electrons by Violet photons
3 0
3 years ago
A police car chases a speeder along a straight road towards a cliff both vehicles move at 160km/h the siren on the police car pr
natta225 [31]

Answer:

f ’= 97.0 Hz

Explanation:

This is an exercise of the doppler effect use the frequency change due to the relative movement of the fort and the observer

in this case the source is the police cases that go to vs = 160 km / h

and the observer is vo = 120 km / h

the relationship of the doppler effect is

          f ’= f₀ (v + v₀ / v- v_{s})

let's reduce the magnitude to the SI system

            v_{s} = 160 km / h (1000 m / 1km) (1h / 3600s) = 44.44 m / s

            v₀ = 120 km / h (1000m / 1km) (1h / 3600s) = 33.33 m / s

we substitute in the equation of the Doppler effect

          f ‘= 100 (330+ 33.33 / 330-44.44)

          f ’= 97.0 Hz

4 0
3 years ago
Silver has a work function of 4.5 eV . Part A What is the longest wavelength of light that will release an electron from a silve
uranmaximum [27]

Answer:

λ = 2.7608 x 10⁻⁷ m = 276.08 nm

Explanation:

The work function of a metallic surface is the minimum amount of photon energy required to release the photo-electrons from the surface of metal. The work function is given by the following formula:

Work Function = hc/λ

where,

Work Function = (4.5 eV)(1.6 x 10⁻¹⁹ J/1 eV) = 7.2 x 10⁻¹⁹ J

h = Plank's Constant = 6.626 x 10⁻³⁴ J.s

c = speed of light = 3 x 10⁸ m/s

λ = longest wavelength capable of releasing electron.

Therefore,

7.2 x 10⁻¹⁹ J = (6.626 x 10⁻³⁴ J.s)(3 x 10⁸ m/s)/λ

λ = (6.626 x 10⁻³⁴ J.s)(3 x 10⁸ m/s)/(7.2 x 10⁻¹⁹ J)

<u>λ = 2.7608 x 10⁻⁷ m = 276.08 nm</u>

7 0
3 years ago
A car starts from rest and accelerates to 14 m/s in 2 seconds. What was its acceleration
Romashka [77]

Answer:

7m/s^2

Explanation:

using v=u+at

since the car started from rest, u=0 , v=14m/s t=2s

a =acceleration.

14=0+a×2

14=0+2a

14=2a

a= 14/2 =7

a=7m/s^2

7 0
2 years ago
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