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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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What does it mean when we say two objects are in equilibrium

cupoosta [38]

An object is considered to be in a condition of equilibrium when it is balanced with regard to all external forces.

Equilibrium:

An object is considered to be in equilibrium if both its angular acceleration and the acceleration of its center of mass are equal to zero. In layman's terms: The item must either be at rest or moving at a constant speed if it is not accelerating because F = ma (force = mass x acceleration). Even in motion, a body can be in equilibrium. This kind of equilibrium is referred to as a dynamic equilibrium.

A weight suspended by a spring or a brick laying on a flat surface is an example. The equilibrium is unstable if the force with the smallest deviation tends to increase the displacement. As an example, imagine a ball bearing on the edge of a razor blade.

Learn more about equilibrium here:

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8 0

2 years ago

Scenario:

katrin [286]

Answer:

Explanation:

5 0

2 years ago

Read 2 more answers

A 90 kg ice skater moving at 12.0 m/s on the ice encounters a region of roughed up ice with a coefficient of kinetic friction of

balandron [24]

Answer:

The skater covers a distance of <u>15 m</u> before stopping.

Explanation:

Let the distance traveled before stopping be 'd' m.

Given:

Mass of the skater (m) = 90 kg

Initial velocity of the skater (u) = 12.0 m/s

Final velocity of the skater (v) = 0 m/s (Stops finally)

Coefficient of kinetic friction (μ) = 0.490

Acceleration due to gravity (g) = 9.8 m/s²

Now, we know that, from work-energy theorem, the work done by the net force on a body is equal to the change in its kinetic energy.

Here, the net force acting on the skater is only frictional force which acts in the direction opposite to motion.

Frictional force is given as:

$f=\mu N$

Where, 'N' is the normal force acting on the skater. As there is no vertical motion, $N=mg$

∴ $f=\mu mg=0.490\times 90\times 9.8=432.18\ N$

Now, work done by friction is a negative work as friction and displacement are in opposite direction and is given as:

$W=-fd=-432.18d$

Now, change in kinetic energy is given as:

$\Delta K=\frac{1}{2}m(v^2-u^2)\\\\\Delta K=\frac{1}{2}\times 90(0-12^2)\\\\\Delta K=45\times (-144)=-6480\ J$

Therefore, from work-energy theorem,

$W=\Delta K\\\\-432.18d=6480\\\\d=\frac{6480}{432.18}\\\\d=14.99\approx 15\ m$

Hence, the skater covers a distance of 15 m before stopping.

7 0

3 years ago

Letícia leaves the grocery store and walks 150.0 m to the parking lot. Then, she turns 90° to the right and walks an additional

Alexxx [7]

Answer:

165.529454

Explanation:

According to the Pythagorean Theorem for calculating the lengths of a right angle triangle's sides, a^2 + b+2 = c^2, where c is the longest side (and the side opposing the right angle). So in your case it would be 150*150 + 70*70 = 27400. And √ 27400 is your answer.

7 0

3 years ago

What height will the object reach? 12 points. Will give brainliest.

umka21 [38]

Answer:

12.7 m

Explanation:

The following data were obtained from the question:

Initial velocity (u) = 56.7 Km/hr

Maximum height (h) =..?

First, we shall convert 56.7 Km/hr to m/s. This can be obtained as follow:

Initial velocity (m/s) = 56.7 x 1000/3600

Initial velocity (m/s) = 15.75 m/s

Next, we shall determine the time taken to get to the maximum height. This can be obtained as follow:

Initial velocity (u) = 15.75 m/s

Final velocity (v) = 0 m/s

Acceleration due to gravity (g) = 9.8 m/s²

Time (t) =?

v = u – gt (since the ball is going against gravity)

0 = 15.75 – 9.8 × t

Rearrange

9.8 × t = 15.75

Divide both side by 9.8

t = 15.75/9.8

t = 1.61 secs.

Finally, we shall determine the maximum height as follow

h = ½gt²

Acceleration due to gravity (g) = 9.8 m/s²

Time (t) = 1.61 secs.

Height (h) =..?

h = ½gt²

h = ½ × 9.8 × 1.61²

h = 4.9 x 1.61²

h = 12.7 m

Therefore, the maximum height reached by the ball is 12.7 m

3 0

3 years ago