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Dima020 [189]
4 years ago
15

A child is stationary on a swing. The child is given a push by his brother to start him swinging. His brother applies a steady f

orce of 84 N over a distance of 0.25 m. Calculate the work done by this force.
Physics
1 answer:
torisob [31]4 years ago
3 0
The formula is M=Fd
so we have F=84N and d=0.25m
Now we just replace F and d into the formula M=84N×0.25m
And the last thing we do is calculate it
M=21Nm
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The kinetic energy of a book on a shelf is equal to the work done to lift the book to the shelf. t/f
Svet_ta [14]
The kinetic energy of a book on a shelf is equal to the work done to lift the book to the shelf is false. The kinetic energy on the shelf is zero because it is not in action.
7 0
3 years ago
Read 2 more answers
A beam of light strikes one face of a window pane with an angle of incidence of 30.0°. The index of refraction of the glass is 1
natka813 [3]

Answer:

(a). The angle of refraction is 19.26°.

(b). That is proved that the rays in air on either side of the glass are parallel to each other

Explanation:

Given that,

Angle of incidence = 30.0°

Index of reflection of glass = 1.52

(a). We need to calculate the angle of refraction for the ray inside the glass

Using snell's law

\dfrac{\sin i}{\sin r}=\mu

\sin r=\dfrac{\sin i}{\mu}

Put the value into the formula

\sin r=\dfrac{\sin 30}{1.52}

r=\sin^{-1}(0.329)

r=19.26^{\circ}

(b). We know that,

The incident ray and emerging ray  is equal then the ray will be parallel.

We need to prove that the rays in air on either side of the glass are parallel to each other

Using formula for emerging ray

\dfrac{\sin e}{\sin r}=\mu

\sin e=\sin r\times \mu

Put the value into the formula

\sin e=0.3289\times 1.52

e=\sin^{-1}(0.499)

e=29.9\approx 30^{\circ}

So, \sin i=\sin e

This is proved.

Hence, (a). The angle of refraction is 19.26°.

(b). That is proved that the rays in air on either side of the glass are parallel to each other

6 0
4 years ago
A teen who weighs 180 pounds normally is standing on a scale inside an elevator The elevator is moving downwards with a constant
nignag [31]

Answer:

174

Explanation:

and 182

7 0
3 years ago
The 3 important steps to a perfect forehand in tennis are : perfect swing, type of racket, and correct finish
Alex17521 [72]

Answer:

False

Explanation:

The 3 important steps to a perfect forehand in tennis are Preparation,Backswing and Swing and contact.

3 0
2 years ago
Adolf and Ed are wearing harnesses and are hanging at rest from the ceiling by means of ropes attached to them. Face to face, th
exis [7]

Answer:

0.78 m

Explanation:

By the conservation of energy, the energy that they gain from potential energy, must be equal to the kinetic energy. So, for Adolf:

Ep = Ek

ma*g*ha = ma*va²/2

Where ma is the mass of Adolf, g is the gravity acceleration (10 m/s²), ha is the height that he reached, and va is the velocity. So:

100*10*0.51 = 100*va²/2

50va² = 510

va² = 10.2

va = √10.2

va = 3.20 m/s

Before the push, both of them are in rest, so the momentum must be 0. The system is conservative, so the momentum after the push must be equal to the momentum before the push:

ma*va + me*ve = 0, where me and ve are the mass and velocity of Ed. So:

100*3.20 + 81ve = 0

81ve = 320

ve = 3.95 m/s

By the conservation of energy for Ed:

me*g*he = me*ve²/2

81*10*he = 81*(3.95)²/2

810he = 631.90

he = 0.78 m

5 0
3 years ago
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