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3 years ago

A car is being lifted by a crane so that it moves upwards at a constant speed.

Physics

1 answer:

anygoal [31]3 years ago

7 0

Answer:

Explanation:

Work done is defined as the product of force and the displacement in the direction of force.

W = F x d x Cos θ

Where, θ be the angle between force and the displacement.

The force of gravity acts downwards and the displacement is in upward, so the angle is 180. cos 180 = -1 , so the work done by the force of gravity is negative.

The force of rope acting in upwards direction and displacement also in upwards direction.

So, the work done is positive

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Select the phrases that correctly describe density. Density is a chemical property. Density relates a mass to its volume. Densit

sp2606 [1]

Answer:

Density relates a mass to its volume.

Density varies with temperature

Density determines if a substance floats or sinks.

Density may have units of grams per milliliter (g/mL)

Explanation:

Density $D$ is a characteristic property of a substance or material and is defined as the relationship between the mass $m$ of a body or substance and the volume $V$ it occupies:

$D=\frac{m}{V}$

This means the density is inversely proportional to the volume.

On the other hand, density is a scalar quantity and according to the International System of Units its unit is $D=\frac{kg}{m^{3}}$ , although it can be also expressed in $\frac{g}{ml}$ .

It should be noted that the density of a body is related to its buoyancy, a substance or body will float on another fluid if its density is lower. In addition, if the pressure of the substance remains constant, as the temperature increases, the density decreases; this means density varies with the temperature as well.

5 0

3 years ago

Two identical twins hold on to a rope, one at each end, on a smooth, frictionless ice surface. They skate in a circle about the

777dan777 [17]

Answer:

Part a)

$L = 2683.2 kg m^2/s$

Part b)

$v' = 8.60 m/s$

Part c)

$W = 4326.7 J$

Explanation:

Part a)

As we know that there is no external torque on the system of two twins

so here we will use

$L = mv r + mvr$

$L = 2(78 \times 4.30 \times 4)$

$L = 2683.2 kg m^2/s$

Part b)

Since angular momentum is conserved here as there is no external torque

so we will have

$2(m v r) = 2( m v' \frac{r}{2})$

$v' = 2v$

$v' = 8.60 m/s$

Part c)

Work done by both of them = change in kinetic energy

so we have

$W = 2(\frac{1}{2}mv'^2 - \frac{1}{2}mv^2)$

$W = m(v'^2 - v^2)$

$W = 78(8.60^2 - 4.3^2)$

$W = 4326.7 J$

5 0

3 years ago

What is the value of the activation energy of the uncatalyzed reaction in reverse?

alexgriva [62]

It would be: Activation Energy = 300 KJ

Hope this helps!

5 0

3 years ago

What is the purpose of a circuit breaker?

sashaice [31]

It’s designed to protect an electrical circuit from damage caused by overcurrent, usually resulting from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected.

That’s really just the basic purpose.
Happy to help!
~Brooke❤️

8 0

3 years ago

I’m steel, the solvent is And the solute is. .

sleet_krkn [62]

Iron is the solvent and carbon is the solute.

8 0

3 years ago