A machine is supplied energy at a rate of 4,000 W and does useful work at a rate of 3,760 W. What is the efficiency of the machine? A. 97 percent B. 96 percent C. 94 percent D. 92 percent

Answer;

Potassium chloride

Explanation;

• Potassium Chloride is an ionic compound and has ionic bond which is stronger than covalent bond in ethyl alcohol,water ,ammonia, and thus has the highest boiling point .
• ionic bond is a type of bond that results from the transfer of electrons between metallic atoms and non-metallic atoms.

1) 31.1 m/s

The rock has been thrown straight out of the window: its motion on the horizontal direction is simply a uniform motion, with constant speed , because no forces act in the horizontal direction. The speed in a uniform motion is given by

where S is the distance traveled and t the time taken.

In this case, the distance by the rock before hitting the ground is and the time taken is , so the initial speed is given by

2) 67.1 m

In this part of the problem we are only interested in the vertical motion of the rock. The vertical motion is a uniformly accelerated motion, with constant acceleration (acceleration of gravity) towards the ground. In a uniformly accelerated motion, the distance traveled by the object is given by

where t is the time. Substituting a=9.8 m/s^2 and t=3.7 s, we can find S, the vertical distance covered by the rock, which corresponds to the height of the 7th floor:

3) 230.1 m

The height of the 7th floor is 67.1 m. So we can assume that the height of each floor is

And so, the height of the 28th floor is

We can find the total time of the fall in this case by using the same formula of the previous part:

In this case, S=268.8 m, so we can re-arrange the formula to find t

And now we can consider the motion of the rock on the horizontal direction: we know that the rock travels at a constant speed of v=31.1 m/s, so the distance traveled is

And this is how far from the building the rock lands.

Answer: Earth is around 150,000,000 km far from the Sun.

Explanation:

Earth is the third planet in Our Solar System which revolves around the Sun.

The distance of Earth from Sun is 149.6 million kilometers which can be approximated to 150 million km.

Using the conversion factor:

Now, converting 150 million km to kilometers, we get:

Hence, Earth is around 150,000,000 km far from the Sun.

Answer: The given statement is false.

Explanation:

Kinetic energy is defined as the energy obtained by an object because of its motion.

For example, moving a pulley on the road.

Whereas energy of an object obtained due to its position is known as potential energy.

For example, lifting a book from table to the shelf shows position of the book has changed.

Therefore, we can conclude that the statement kinetic energy of a book on a shelf is equal to the work done to lift the book to the shelf, is false.