What is the average velocity of a car that travels 450 km north in 9.0 hours?

Please help i don't understand

IrinaVladis [17]

The answer is C why because I know it is

3 0

3 years ago

Which of the following scenarios describes an object being acted on by a conservative force?

andrew11 [14]

Answer:

Option: A feather falls from one end of a tube to the other inside a vacuum.

Explanation:

To answer the question we need to first understand what is meant by Conservative Force.

In principle, Conservative forces are basically forces that are not affected by outside parameters (such as friction, air resistance etc). If the present force is strictly based on the initial and the final location of the object, with the inbetween path being irrelevant, the force will be conservative. A conservative force will be zero if we are looking at a closed path-system. We can also say that the system's energy loss will not be a function of the distance covered but is a function of displacement.

Looking at the available options, we can see that:

Option A: A woman hikes up a mountain to a point 20 feet above ground.

This is a Non Conservative force as this case does not depend just on displacement but also in the path in between, i.e. hiking up the mountain there will be other forces that will affect the woman such as air resistance.

Option B: A dishwasher was pulled up to a window by a rope, using a pulley system.

This is a Non Conservative force as this case does not depend just on displacement but also in the inbetween path along with the forces present in a pulley system such as friction.

Option C: A feather falls from one end of a tube to the other inside a vacuum.

This is a Conservative force as here we are looking at a vacuum and its a closed system of no other forces present due to vacuum. However, we CAN'T say that ALL forces in a Vacuum Are Conservative because there are cases of dynamic steady state fields where the system is prone to other forces (i.e. open system).

Option D: A puck glides across and slowly comes to a stop on an ice rink.

This is a Non Conservative force as this case does not depend just on displacement but also the motion until it comes to a stop, which is possibly due to the friction between the ice rink and the puck.

7 0

3 years ago

A girl pushes a 1.04 kg book across a table with a horizontal applied force 10 points

mr Goodwill [35]

Answer:

Approximately $11.0\; \rm m \cdot s^{-1}$ . (Assuming that $g = 9.81 \; \rm N \cdot kg^{-1}$ , and that the tabletop is level.)

Explanation:

Weight of the book:

$W = m \cdot g = 1.04 \; \rm kg \times 9.81\; \rm N \cdot kg^{-1} \approx 10.202\; \rm N$ .

If the tabletop is level, the normal force on the book will be equal (in magnitude) to weight of the book. Hence, $F(\text{normal force}) \approx 10.202\; \rm N$ .

As a side note, the $F_N$ and $W$ on this book are not equal- these two forces are equal in size but point in the opposite directions.

When the book is moving, the friction $F(\text{kinetic friction})$ on it will be equal to

$\mu_{\rm k}$ , the coefficient of kinetic friction, times
$F(\text{normal force})$ , the normal force that's acting on it.

That is:

$\begin{aligned}& F(\text{kinetic friction}) \\ &= \mu_{\rm k}\cdot F(\text{normal force})\\ &\approx 0.35 \times 10.202\; \rm N \approx 3.5708\; \rm N\end{aligned}$ .

Friction acts in the opposite direction of the object's motion. The friction here should act in the opposite direction of that $15.0\; \rm N$ applied force. The net force on the book shall be:

$\begin{aligned}& F(\text{net force}) \\ &= 15.0 \; \rm N - F(\text{kinetic friction}) \\& \approx 15.0 - 3.5708\; \rm N \approx 11.429\; \rm N\end{aligned}$ .

Apply Newton's Second Law to find the acceleration of this book:

$\displaystyle a = \frac{F(\text{net force})}{m} \approx \frac{11.429\; \rm N}{1.04\; \rm kg} \approx 11.0\; \rm m \cdot s^{-2}$ .

6 0

3 years ago

What is the relation between inertia and mass?

aleksandr82 [10.1K]

Answer:

The tendency of an object to resist changes in its state of motion varies with mass. Mass is that quantity that is solely dependent upon the inertia of an object. The more inertia that an object has, the more mass that it has. A more massive object has a greater tendency to resist changes in its state of motion.

Explanation:

8 0

3 years ago

A 230-km-long high-voltage transmission line 2.0 cm in diameter carries a steady current of 1,100 A. If the conductor is copper

Molodets [167]

Answer:

28.23 years

Explanation:

I = 1100 A

L = 230 km = 230, 000 m

diameter = 2 cm

radius, r = 1 cm = 0.01 m

Area, A = 3.14 x 0.01 x 0.01 = 3.14 x 10^-4 m^2

n = 8.5 x 10^28 per cubic metre

Use the relation

I = n e A vd

vd = I / n e A

vd = 1100 / (8.5 x 10^28 x 1.6 x 10^-19 x 3.14 x 10^-4)

vd = 2.58 x 10^-4 m/s

Let time taken is t.

Distance = velocity x time

t = distance / velocity = L / vd

t = 230000 / (2.58 x 10^-4) = 8.91 x 10^8 second

t = 28.23 years

5 0

3 years ago

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