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3 years ago

10

Consider what happens when you jump up in the air. which of the following is the most accurate statement?

1 answer:

slega [8]3 years ago

6 0

1.It is the upward force exerted by the ground that pushes you up, but this force can never exceed your weight.

2) You are able to spring up because the earth exerts a force upward on you that is stronger than the downward force you exert on the earth.

3) When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air.

4) When you jump up the earth exerts a force F1 on you and you exert a force F2 on the earth. You go up because F1 > F2.

<span>5) Since the ground is stationary, it cannot exert the upward force necessary to propel you into the air. Instead, it is the internal forces of your muscles acting on your body itself that propels the body into the air.</span>

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Tanzania [10]

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B

Explanation:

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3 years ago

Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. In one test, t

kkurt [141]

Answer:

$t=0.038s$

Explanation:

Project mass m=3.8 kg

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To find

Time t

Solution

From Newtons second law we know that

∑F=ma

Where m is mass

a is acceleration

We can write this equation as

∑F=m(Δv/Δt)

$=m\frac{v_{f}-v_{i}}{t}$

Rearrange this equation to find time t

So

$t=m\frac{v_{f}-v_{i}}{F}$

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$t=3.8kg\frac{9.3*10^3m/s-0}{9.3*10^5N} \\t=0.038s$

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3 years ago

A person's body is producing energy internally due to metabolic processes. If the body loses more energy than metabolic processe

SVETLANKA909090 [29]

Answer:

$T_s = 6.8 degree C$

Explanation:

As per thermal radiation we know that rate is heat radiation is given as

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here we know that

T = 34 degree C = 307 K

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$\sigma = 5.67 \times 10^{-8} W/m^2K^4$

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now we have

$120 = (5.67 \times 10^{-8})(0.557)(1.38)(307^4 - T_s^4)$

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3 years ago

Use the definition of scalar product, a overscript right-arrow endscripts times b overscript right-arrow endscripts = ab cos θ,

makkiz [27]

Answer: $\theta=cos^{-1}0.991=7.69^o$

The following vectors have been given: $\vec{a}=3.0\widehat{i}+3.0\widehat{j}+3.0\widehat{k}\\ \vec{b}=5.0\widehat{i}+7.0\widehat{j}+6.0\widehat{k}$

The angle between these two vectors can be found by:

$cos\theta=\frac{\vec{a}.\vec{b}}{||\vec{a}|| ||\vec{b}||}\\
||\vec{a}=\sqrt{a_x^2+a_y^2+a_z^2}$

$\vec{a}.\vec{b}=a_xb_x+a_yb_y+a_zb_z\\ \vec{a}.\vec{b}=3\times5+3\times7+3\times6=15+21+18=54$

$||\vec{a}||=\sqrt{3^2+3^2+3^2}=\sqrt{27}\\ ||\vec{b}||=\sqrt{5^2+7^2+6^2}=\sqrt{110}$

$cos\theta=\frac{54}{\sqrt{27}\times\sqrt{110}}\\=0.991\\ \Rightarrow \theta=cos^{-1}0.991=7.69^o$

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3 years ago

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bulgar [2K]

Joules is used for work.

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3 years ago