As potential and kinetic energy increase what happens to mechanical energy?

A box is against a wall. A person pushes on the box, but the box does not move. Is this situation an example of a force

Leya [2.2K]

Answer: I don’t think so, because the box is ALREADY against the wall so you can’t move it further into the wall

Explanation:

7 0

3 years ago

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A tank whose bottom is a mirror is filled with water to a depth of 20.0 cm. A small fish floats motionless 7.0 cm under the surf

liberstina [14]

Answer:

The apparent depth of (a) the fish is 5.3 cm and (b) the image of the fish is 24.8 cm.

Explanation:

According to the following equation:

$\frac{n_{w} }{s} +\frac{n_{a} }{s'} = \frac{n_{a}- n_{w}}{R_{c} } \\$

where nw and na is the refractive indices of water (1.33) and air (1.00) respectively; s is the depth of the fish below the surface of the water; s' is the apparent depth of the fish from normal incidence and Rc is the radius of curvature of the mirror at the bottom of the tank.

Note that the bottom of the tank is assumed to be a flat mirror, therefore the radius of curvature is very large (R⇒∞).

Therefore, the above equation can be expressed as:

$\frac{n_{w}}{s} +\frac{n_{a}}{s'}=0$

Now we can solve for the apparent depth of the fish.

(a) $s'=-(\frac{n_{a}}{n_{w}})x s$ (Make s' subject of the formula from the above equation)

$s'=(\frac{1.00}{1.33} )x7cm$

∴ $s'=5.3 cm.$

(b) The motionless fish floats 13 cm above the mirror, therefore the image of the fish will be situated at 13 + 20 =33 cm away from the real fish.

Therefore, s = 33 cm

$s'=-(\frac{n_{a}}{n_{w}})x s$

$s'=(\frac{1.00}{1.33} )x 33 cm$

$s'=24.8 cm.$

NB: Here, it is assumed that the water is pure, as impurities may alter the refractive index of water.

8 0

4 years ago

A 50 kg cheetah has 3,600 J of kinetic energy. What is its velocity?

stira [4]

To determine the velocity, let us use the equation:

v = √ $\frac{2K}{m}$

The kinetic energy (K) is equivalent to 3,600 J, and mass (m) is equivalent to 50kg. Let us now solve for velocity.

v = √ $\frac{2K}{m}$
v = √ $\frac{2 (3,600 J)}{50 kg}$
v = √ $\frac{7,200}{50}$
v = √144
v = 12

The velocity of the tiger is 12 meter/second.

4 0

3 years ago

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A 200-Ω resistor is connected in series with a 10-µF capacitor and a 60-Hz, 120-V (rms) line voltage. If electrical energy costs

Vika [28.1K]

Answer:

Cost to leave this circuit connected for 24 hours is $ 3.12.

Explanation:

We know that,

$\mathrm{X}_{\mathrm{c}}=\frac{1}{2 \pi \mathrm{fc}}$

f = frequency (60 Hz)

c= capacitor (10 µF = $10^-6$ )

$\mathrm{X}_{\mathrm{c}}=\text { Capacitive reactance }$

Substitute the given values

$\mathrm{X}_{\mathrm{c}}=\frac{1}{2 \times 3.14 \times 10 \times 10^{-6} \times 60}$

$\mathrm{X}_{\mathrm{c}}=\frac{1}{3.768 \times 10^{-3}}$

$\mathrm{x}_{\mathrm{c}}=265.39 \Omega$

Given that, R = 200 Ω

$X^{2}=R^{2}+X c^{2}$

$X^{2}=200^{2}+265.39^{2}$

$X^{2}=40000+70431.85$

$X^{2}=110431.825$

$x=\sqrt{110431.825}$

X = 332.31 Ω

$\text { Current }(I)=\frac{V}{R}$

$\text { Current }(I)=\frac{120}{332.31}$

Current (I) = 0.361 amps

“Real power” is only consumed in the resistor,

$\mathrm{I}^{2} \mathrm{R}=0.361^{2} \times 200$

$\mathrm{I}^{2} \mathrm{R}=0.1303 \times 200$

$\mathrm{I}^{2} \mathrm{R}=26.06 \mathrm{Watts} \sim 26 \mathrm{watts}$

In one hour 26 watt hours are used.

Energy used in 54 hours = 26 × 24 = 624 watt hours

E = 0.624 kilowatt hours

Cost = (5)(0.624) = 3.12

3 0

3 years ago

Which of the following statement is FALSE about momentum? (Consider the formula p = mv .)

Kaylis [27]

"A less massive object can never have more momentum than a more massive object."

That statement is FALSE, because momentum doesn't only depend on mass alone. It also depends on the speed with which the mass is moving. If the less massive object is moving at a tremendous speed, then it's quite possible for it to have more momentum than a more massive object.

A nice example is: A brick wall. The brick wall is not moving at all. Its speed is zero, so it has NO momentum. An ant crawling along on top of the brick wall has more momentum than the brick wall itself has.

7 0

3 years ago