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4 years ago

What force is necessary to accelerate a 70-kg object at a rate of 4.2 m/s2 ? Show your wo k below?

Physics

1 answer:

Naily [24]4 years ago

4 0

Newton's 2nd law of motion:

   Force = (mass) x (acceleration)

   = (70 kg) x (4.2 m/s²)

   = (70 x 4.2) kg-m/s²

   =    294 newtons .

A picture of my wok is attached below.

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Liquids and gases transfer heat by ____.

vodka [1.7K]

Fluids always transfer heat by convection. So, your answer is B. That's how a oven works actually!

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4 years ago

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Two electronics technicians are discussing conductors and insulators. Technician A says that conductors have more free electrons

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Technician A is Correct.

You can see this when he says that conductors have more free electrons than insulators. This statement is True.

While Technician B says that, insulators have the lower resistance than conductors. This statement is False.

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Find the net rate of heat transfer by radiation in watts from a skier standing in the shade, given the following. She is complet

fomenos

Answer:

-34.5 W

Explanation:

rate of heat transfer = Stefan-Boltzmann constant x emissivity x surface area x temperature^4

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3 years ago

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.

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3 years ago

PLZ HELP why do the planets move in a way that promotes life?

CaHeK987 [17]

Answer:

Because plant means a life. Plants need foods and energy as same as human. So for a plant mostly need sun light and water.

They need water because water is collected through root of the plant and absorbed from the soil.

They need sun light because do the process of photosynthesis and plants need other gasses well as water and sun light for live and survive.

Explanation:

Hope i helped u...

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3 years ago