Answer:
Option e) 320 s
Explanation:
Here, distance = 3.0 km = 3000 m
The velocity of boat when it is going upstream;
Upstream velocity = velocity of boat in still water - velocity of river flow
So, Upstream velocity 
So,Time to go upstream

The velocity of boat when it is going downstream;
Downstream velocity = velocity of boat in still water + velocity of river flow
So, Downstream velocity 
So,Time to go downstream

So, total time (t) = 
Option E is the correct answer.
A. The molecules start packed together very tightly in a solid. Then when it turns to water, the molecules can move around each other freely, but still contained. When water turns to vapor, the molecules are going crazy moving around. They are not contained at all and bounce of of each other freely.
b. The temperature rises. (ice turns to water at 33 degrees and water turns to vapor at 212 degrees)
Complete question:
It is measured that 3/4 of a body's volume is submerged in oil of density 800kg/m³. What is the specific gravity of oil?
Answer:
The specific gravity of the oil is 0.8.
Explanation:
Given;
density of the oil,
= 800 kg/m³
density of water,
= 1000 kg/m³
The specific gravity of any substance is the ratio of the substance density to the density of water.
Specific gravity of the oil = density of the oil / density of water
Specific gravity of the oil = 800/1000
Specific gravity of the oil = 0.8
Therefore, the specific gravity of the oil is 0.8.
False, there are always pros and cons to research
<h3>1)</h3>
No,kinetic energy cannot be negative since its given by KE=mv²,mass cannot be negative and the square of speed cannot b negative.
<h3>2)</h3>
Yes,any force opposing motion or displacement does negative work. They are often referred to as resistive forces (friction,air resistance,drag...)
<h3>3)</h3>
Nope it does not, it just forces the object to move in a circular path known as a centripetal force. It can accelerate an object by changing it's direction but not it's speed.
<h3>4)</h3>
No it cannot,If an object is sliding on the table (assuming it is not an incline), then most probably that normal force cancels out the weights effect or assuming there is an incline, it cancels the weight's y component.
<h3>5)</h3>

The work done is zero
<h3>6)</h3>

The work is just the product of the magnitude of the force exerted and the displacement of the object.
<h3>7)</h3>

<h3>Work is decreasing but positive</h3>
<h3>8)</h3>

<h3>Work is zero</h3>
<h3>9)</h3>

<h3>Work is negative</h3>