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2 years ago

A sled of mass 8 kg slides along the ice. It has an initial speed of 4 m/s but

Physics

1 answer:

marysya [2.9K]2 years ago

6 0

As our story begins, the sled ... whose mass is 8 kg ... is sliding along the ice at a speed of 4 m/s.

The sled's kinetic energy is (1/2 m v²) = (4 kg · 16 m²/s²) = 64 J .

After what seems like only the blink of an eye, the sled is no longer sliding. It is stationary. Motionless. At Rest. Just sitting there !

Its speed has been reduced to zero and ... because kinetic energy is the energy of motion ... the sled's kinetic energy is now also zero. Sixty-four Joules of energy have disappeared !

How can this be ? ! ? We know that energy is conserved. It can never just appear out of nothing, and it can never just disappear into nothing. If energy suddenly appears, it had to come from somewhere, and if energy suddenly disappears, it had to go somewhere. So where did our 64 Joules of kinetic energy go ?

It went into the ice, THAT's where ! We can say that the sled did 64J of work, and melted a thin slick layer of water on the surface of the ice. OR we can say that friction did NEGATIVE 64J of work on the sled, to cancel the 64J that it had originally, sap its kinetic energy, and bring it to rest.

I think <em>choice-B</em> was supposed to say "<em>B. -64J</em>", but somebody typed it sloppily and neglected to proofread it before posting.

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A parallel-plate vacuum capacitor has 8.60 J of energy stored in it. The separation between the plates is 3.80 mm . If the separ

creativ13 [48]

Answer:

Part a)

$E = \frac{8.60}{2.62} = 3.28 J$

Part b)

$E = 2.62(8.60) = 22.5 J$

Explanation:

As we know that the energy of capacitor when it is not connected to potential source is given as

$U = \frac{Q^2}{2C}$

As we know that initial energy is given as

$8.60 = \frac{Q^2}{2C}$

now we know that capacitance of parallel plate capacitor is given as

$C = \frac{\epsilon_0A}{d}$

now the new capacitance when distance is changed from 3.80 mm to 1.45 mm

$C' = \frac{Cd}{d'}$

$C' = \frac{C(3.80)}{1.45}$

$C' = 2.62 C$

Now the new energy of the capacitor is given as

$E = \frac{Q^2}{2(2.62C)}$

$E = \frac{8.60}{2.62} = 3.28 J$

Part b)

Now if the voltage difference between the plates of capacitor is given constant

now the energy energy of capacitor is

$U = \frac{1}{2}CV^2$

$8.60 = \frac{1}{2}CV^2$

now when capacitance is changed to new value then new energy is given as

$E = \frac{1}{2}C'V^2$

$E = \frac{1}{2}(2.62C)V^2$

$E = 2.62(8.60) = 22.5 J$

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3 years ago

Convert 800 cm to meters.

Rasek [7]

Answer:8 meters

Explanation:100cm is a meter

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2 years ago

Read 2 more answers

If the man on the left pulls on the object with a force of 500 N and the man on the right pulls on the object with a force of 75

Igoryamba

Force is a vector quantity
so pulling from opposite side will be negative
so
750+(-500)= 250N
C is the right answer
becauseause the man on the right applies greater force.

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Bezzdna [24]

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