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2 years ago

5

A big box of sausages (30 kg) is lifted from the ground to the top shelf of the freezer. If the box is lifted at a constant spee

d, a distance of 1.75 m, what work is done against gravity?

1 answer:

Lubov Fominskaja [6]2 years ago

5 0

Answer:

Work done to lift the box is 515.03 J

Explanation:

By work energy theorem we know that work done by all forces is equal to change in kinetic energy

So we have

$W_g + W_{ex} = \Delta K$

so we have

$-mgh + W_{ex} = 0$

so we have

$W_{ex} = mgh$

$W_{ex} = 30(9.8)1.75$

$W_{ex} = 515.03 J$

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A square block of steel with volume 10 cm3 and mass of 75 g is cut precisely in half. The density of the two smaller pieces is n

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A. Density only depends on the substance. It doesn't matter whether you have a little chip of it or a supertanker full of it ... the density doesn't change.

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2 years ago

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A ball is falling at terminal velocity. Terminal velocity occurs when the ball is in equilibrium and the forces are balanced. Wh

Greeley [361]

Answer:

A free body diagram with 2 forces: the first pointing downward labeled F Subscript g Baseline 20 N and the second pointing upward labeled F Subscript air Baseline 20 N.

Explanation:

This is because at terminal velocity, the ball stops accelerating and the net force on the ball is zero. For the net force to be zero, equal and opposite forces must act on the ball, so that their resultant force is zero. That is F₁ + F₂ = 0 ⇒ F₁ = -F₂

Since F₁ = 20 N, then F₂ = -F₁ = -20 N

So, if F₁ points upwards since it is positive, then F₂ points downwards since it is negative.

So, a free body diagram with 2 forces: the first pointing downward labeled F Subscript g Baseline 20 N and the second pointing upward labeled F Subscript air Baseline 20 N best describes the ball falling at terminal velocity.

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2 years ago

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A stone falls from rest from the top of a cliff. A second stone is thrown downward from the same height 2.7 s later with an init

Darina [25.2K]

Answer:4.05 s

Explanation:

Given

First stone is drop from cliff and second stone is thrown with a speed of 52.92 m/s after 2.7 s

Both hit the ground at the same time

Let h be the height of cliff and it reaches after time t

$h=\frac{gt^2}{2}$

For second stone

$h=52.92\times \left ( t-2.7\right )+\frac{g\left ( t-2.7\right )^2}{2}$ ---2

Equating 1 &2 we get

$\frac{gt^2}{2}=52.92\times \left ( t-2.7\right )+\frac{g\left ( t-2.7\right )^2}{2}$

$\frac{g}{2}\left ( t-t+2.7\right )\left ( 2t-2.7\right )-\left ( t-2.7\right )52.92=0$

$13.23\times \left ( 2t-2.7\right )-\left ( t-2.7\right )52.92=0$

$26.46t-35.721-52.92t+142.884=0$

$t=4.05 s$

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2 years ago

If a metallic wire of cross sectional area 3.0 ´ 10-6 m2 carries a current of 6.0 A and has a mobile charge density of 4.24 ´ 10

elena-14-01-66 [18.8K]

Answer:

The drift velocity is $v_d=2.9\times 10^{-4}\ m/s.$

Explanation:

Given :

Area of metallic wire, $A = 3\times 10^{-6}\ m^2$ .

Current through wire , $I=6 \ A.$

Mobile charge density , $n=4.24\times 10^{28} \ carriers/m^3.$

Charge value , $e=1.6\times 10^{-19}\ C.$

We need to find drift velocity , $v_d.$

Now, we know :

$I=neAv_d$

Therefore, $v_d=\dfrac{I}{neA}$

Putting all given values in above equation we get,

$v_d=\dfrac{6}{4.24\times 10^{28}\times 1.6\times 10^{-19} \times 3 \times 10^{-6}}$

$v_d=2.9\times 10^{-4}\ m/s.$

Hence, this is the required solution.

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A climatograph for a tropical grassland or savanna would look different from the climatograph shown for a temperate grassland. D

Savatey [412]

Answer:

Savannas have a fairly constant temperature all year; temperate grasslands have a greater seasonal temperature variation.

Explanation:

For example, the African Savanna has an almost constant temperature all year (see the first figure below).

The difference between summer and winter temperatures is only about 5 °C, and the rate of temperature change is quite slow.

The temperature of a temperate grassland (see the second figure below) has a much greater seasonal variation.

The summers are hot, and the winters are cold. The difference between summer and winter temperatures is about 30 °C, with a rapid rate of temperature change from one season to the next.

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2 years ago