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3 years ago

If the sign of work is negative,

Physics

1 answer:

aivan3 [116]3 years ago

5 0

If the sign of work is negative, that means the force and the motion are in opposite directions.

Let's say you see something roll off of the shelf. You catch it, and you let it down slowly and gently.

Gravity exerted down-force on it and it moved down. Gravity did positive work on it.

YOU exerted UP-force on it and it moved down. YOU did negative work on it.

(Also, the falling object exerted down-force on your hand, and your hand moved down. The falling object did positive work on your hand ! Where did THAT energy come from ? It came from the potential energy that the object had while it was on the shelf. Your hand absorbed that energy on the way down, doing negative work. So the object didn't have any kinetic energy when it reached the floor, and it did NOT splinter the floor or shatter in smithereens. It had barely enough energy left to make a sound when it hit the floor.)

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Why do astronauts need to wear pressurized suits in space?

SashulF [63]

The correct answer is C , because the space is vacuum and his body can explode and for this reason, the astronaut need a special costum to be protected. It's the same on the moon, because there is no atmosphere

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3 years ago

Lightning a. occurs when a positively charged cloud base induces a negative charge on the Earth's surface. b. travels most often

mart [117]

Answer:

c. may be accompanied by the sound of explosively expanding hot air, called thunder.

Explanation:

Lightning is a discharge which is due to the reaction between oppositely charged charges in the clouds, or between clouds base and the Earth surface.

The motion of the cloud causes charging of clouds by friction, thus the reaction between opposite charges (jumping of charges from one cloud to another) in the cloud can lead to lightning. Also, oftentimes the bottom of a cloud is negatively charged so that this is attracted to the positive charge on the earth surface. Thus leading to a discharge called lightning.

Thus in the given question, the appropriate option is C. This implies that, lightning may be accompanied by the sound of explosively expanding hot air, called thunder.

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3 years ago

How could you increase the kinetic energy of a wagon without increasing it's mass

Zarrin [17]

Answer:

send the wagon down a higher hill

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3 years ago

Read 2 more answers

Si un ciclista se mueve a una velocidad de 5 m/s y acelera 1 m/s2, a los 10 segundos su velocidad será

MrRa [10]

Answer:

A los 10 segundos su velocidad será 15 $\frac{m}{s}$

Explanation:

La aceleración de un objeto es una magnitud que indica cómo cambia la velocidad del objeto en una unidad de tiempo.

En otras palabras, la aceleración relaciona los cambios de la velocidad con el tiempo en el que se producen, es decir que mide cómo de rápidos son los cambios de velocidad:

Una aceleración grande significa que la velocidad cambia rápidamente.
Una aceleración pequeña significa que la velocidad cambia lentamente.
Una aceleración cero significa que la velocidad no cambia.

La aceleración "a" puede ser calculada mediante la expresión:

$a=\frac{vfinal - vinicial}{tiempo}$

En este caso:

a= 1 $\frac{m}{s^{2} }$

vfinal= ?
vinicial= 5 $\frac{m}{s}$
tiempo= 10 s

Reemplazando:

$1\frac{m}{s^{2} }=\frac{vfinal - 5\frac{m}{s} }{10 s}$

Resolviendo se obtiene:

1 $\frac{m}{s^{2} }$ *10 s= vfinal - 5 $\frac{m}{s}$

10 $\frac{m}{s}$ = vfinal - 5 $\frac{m}{s}$

10 $\frac{m}{s}$ + 5 $\frac{m}{s}$ = vfinal

15 $\frac{m}{s}$ = vfinal

A los 10 segundos su velocidad será 15 $\frac{m}{s}$

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3 years ago

Dry cells become soft even when not in use. Explain.

mamaluj [8]

This is possible due to self-discharge. Very small internal currents inevitably occur in these cells over time and they will eventually exhaust the chemistry.

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3 years ago