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3 years ago

6

An electron is accelerated from rest through a potential difference. After acceleration the electron has a de Broglie wavelength

of 880 nm. What is the potential difference though which this electron was accelerated

1 answer:

Vladimir [108]3 years ago

4 0

Answer:

3x10⁴v

Explanation:

Using

Wavelength= h/ √(2m.Ke)

880nm = 6.6E-34/√ 2.9.1E-31 x me

Ke= 6.6E-34/880nm x 18.2E -31.

5.6E-27/18.2E-31

= 3 x 10⁴ Volts

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Drops of rain fall perpendicular to the roof of a parked car during a rainstorm. The drops strike the roof with a speed of 15 m/

IrinaK [193]

Answer: (a) 1.065 N (b) 2.13 N

Explanation:

<h2>(a) average force exerted by the rain on the roof</h2><h2 />

According Newton's 2nd Law of Motion the force $F$ is defined as <u>the variation of linear momentum</u> $p$ <u>in time:</u>

$F=\frac{dp}{dt}$ (1)

Where the linear momentum is:

$p=mV$ (2) Being $m$ the mass and $V$ the velocity.

In the case of the rain drops, which initial velocity is $V_{i}=15m/s$ and final velocity is $V_{f}=0$ (we are told the drops come to rest after striking the roof). The momentum of the drops $p_{drops}$ is:

$p_{drops}=mV_{i}+mV_{f}$ (3)

If $V_{f}=0$ , then:

$p_{drops}=mV_{i}$ (4)

Now the force $F_{drops}$ exerted by the drops is:

$F_{drops}=\frac{dp_{drops}}{dt}=\frac{d}{dt}mV_{i}$ (5)

$F_{drops}=\frac{dm}{dt}V_{i}+m\frac{dV_{i}}{dt}$ (6)

At this point we know the mass of rain per second (mass rate) $\frac{dm}{dt}=0.071 kg/s$ and we also know the initial velocity does not change with time, because that is the velocity at that exact moment (instantaneous velocity). Therefore is a constant, and the derivation of a constant is zero.

This means (6) must be rewritten as:

$F_{drops}=\frac{dm}{dt}V_{i}$ (7)

$F_{drops}=(0.071 kg/s)(15m/s)$ (8)

$F_{drops}=1.065kg.m/s^{2}=1.065N$ (9) This is the force exerted by the rain drops on the roof of the car.

<h2>(b) average force exerted by hailstones on the roof </h2><h2 />

Now let's assume that instead of rain drops, hailstones fall on the roof of the car, and let's also assume these hailstones bounce back up off after striking the roof (this means they do not come to rest as the rain drops).

In addition, we know the hailstones fall with the same velocity as the rain drops and have the same mass rate.

So, in this case the linear momentum $p_{hailstones}$ is:

$p_{hailstones}=mV_{i}+mV_{f}$ (9) Being $V_{i}=V_{f}$

$p_{hailstones}=mV+mV=2mV$ (10)

Deriving with respect to time to find the force $F_{hailstones}$ exerted by the hailstones:

$F_{hailstones}=\frac{d}{dt}p_{hailstones}=\frac{d}{dt}(2mV)$ (10)

$F_{hailstones}=2\frac{d}{dt}(mV)=2(\frac{dm}{dt}V+m\frac{dV}{dt})$ (11)

Assuming $\frac{dV}{dt}=0$ :

$F_{hailstones}=2(\frac{dm}{dt}V)$ (12)

$F_{hailstones}=2(0.071 kg/s)(15m/s)$ (13)

Finally:

$F_{hailstones}=2.13kg.m/s^{2}=2.13N$ (14) This is the force exerted by the hailstones

Comparing (9) and (14) we can conclude the force exerted by the hailstones is two times greater than the force exerted by the raindrops.

5 0

3 years ago

A 0.5 kg ball moves in a circle that is 0.4 m in radius at a speed of 4.0 m/s. Calculate its centripetal acceleration. (40 m/s2)

Mkey [24]

Centripetal acceleration is the acceleration of an object that is moving in a circular motion. It is calculated by dividing the square of the velocity to the radius of the circular path. It is calculated as follows:

a = v^2 / r = 4.0^2 / 0.4 = 40 m/s^2

8 0

3 years ago

A ball has mass of 140g. what is the force to accelerate the ball at 25m/s

Fittoniya [83]

We know, F = m * a

Here, m = 140 g = 0.140 Kg

a = 25 m/s2

It would be: F = 0.140 * 25 = 3.5 N

So your answer would be 3.5N

6 0

3 years ago

Read 2 more answers

A car travels for 50mph for 5 hours, then for 30mph for another 3 hours in the same direction. What is the average speed the mot

pshichka [43]

Answer:

42.5mph

Explanation:

The computation of the average speed is shown below:

As we know that

Speed = Distance ÷ Time

ANd, distance = Speed × time

So, the distance would be

= (50 × 5 hours) + (30 × 3)

= 250 + 90

= 340 miles

And, the total time taken is 8 hours

So, the average speed is

= 340 miles ÷ 8 hours

= 42.5mph

5 0

3 years ago

When adjusting the tightness of a string ,we are changing its

Elanso [62]

Answer:

Tension.

Explanation:

The tighter a string is, the more tension is applied to it; the more loose a string is, less tension is applied to it.

Therefore, when you adjust the tightness of a string you are tackling with it's tension.

Hope it helped,

BiologiaMagister

4 0

3 years ago