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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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What do electric forces between charges depend on

denis23 [38]

Answer:

On the magnitude of the charges, on their separation and on the sign of the charges

Explanation:

The magnitude of the electric force between two charges is given by

$F=k\frac{q_1 q_2}{r^2}$

where

k is the Coulomb's constant

q1, q2 are the magnitudes of the two charges

r is the separation between the charges

From the formula, we see that the magnitude of the force depends on the following factors:

- magnitude of the two charges

- separation between the charges

Moreover, the direction of the force depends on the sign of the two charges. In fact:

- if the two charges have same sign, the force is repulsive

- if the two charges have opposite signs, the force is attractive

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3 years ago

One mole of ideal gas is slowly compressed to one-third of its original volume. in this compression, the work done on the gas ha

beks73 [17]

A boiling pot of water (the water travels in a current throughout the pot), a hot air balloon (hot air rises, making the balloon rise) , and cup of a steaming, hot liquid (hot air rises, creating steam) are all situations where convection occurs.
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3 years ago

Radar uses radio waves of a wavelength of 2.4 ${\rm m}$ . The time interval for one radiation pulse is 100 times larger than t

blondinia [14]

Answer:

120 m

Explanation:

Given:

wavelength 'λ' = 2.4m

pulse width 'τ'= 100T ('T' is the time of one oscillation)

The below inequality express the range of distances to an object that radar can detect

τc/2 < x < Tc/2 ---->eq(1)

Where, τc/2 is the shortest distance

First we'll calculate Frequency 'f' in order to determine time of one oscillation 'T'

f = c/λ (c= speed of light i.e 3 x $10^{8}$ m/s)

f= 3 x $10^{8}$ / 2.4

f=1.25 x $10^{8}$ hz.

As, T= 1/f

time of one oscillation T= 1/1.25 x $10^{8}$

T= 8 x $10^{-9}$ s

It was given that pulse width 'τ'= 100T

τ= 100 x 8 x $10^{-9}$ => 800 x $10^{-9}$ s

From eq(1), we can conclude that the shortest distance to an object that this radar can detect:

$x_{min}$ = τc/2 => (800 x $10^{-9}$ x 3 x $10^{8}$ )/2

$x_{min}$ =120m

8 0

3 years ago

For the simple harmonic motion equation

My name is Ann [436]

Given that : d = 5sin(pi t/4), So, maximum displacement, d = 5*(+1) = 5 Also, maximum displacement, d = 5*(-1) = -5

3 0

3 years ago

A river flows at 2m/s. The velocity of a ferry relative to the shore is 4m /s at right angle to the current. What is the velocit

monitta

The velocity of the ferry relative to the current is 4.5 m/s.

<h3>Relative velocity</h3>

Relative velocity is the velocity of a body as observed from the reference point of another body either stationary or in motion.

Since the river is flowing parallel to the shore and the ferry is moving perpendicular to the shore, their velocities are at right angles to each other.

The two velocities form a right angled-triangle of sides 2, 4 and a hypotenuse which gives the relative velocity of the ferry to the current.

Using Pythagoras rule:

c² = a² + b²

Let c be the hypotenuse
a = velocity of the ferry, and
b = the velocity of the current, and

c² = 4² + 2²

c² = 16 + 4

c = 20

c = √20

c = 4.47 m/s

c ≈ 4.5 m/s

Therefore, the velocity of the ferry relative to the current is 4.5 m/s.

Learn more about relative velocity and Pythagoras rule at: brainly.com/question/25617868

5 0

2 years ago