Answer:
b. Friction decreased when he went from pavement to ice and then increased two more times.
Explanation:
Frictional force depends on the normal force of the surface and a friction coefficient.
Since we're talking about the same car, the value of 
will remain constant whereas μ will represent the change in the frictional coefficient of the surface. Now we consider the different surfaces, cars will slide in an icy road which means that the frictional coefficient is smaller than the pavement.
After Joshua returns to the pavement road, the resulting frictional force increases and will do so one more time when he reaches the gravel road. Gravel roads have greater frictional coefficients than pavement roads which means the frictional force will increase a second time.
Answer:
An increase in air temperature because of its compression.
Explanation:
The Gay-Lussac's Law states that a gas pressure is directly proportional to its temperature in an enclosed system to constant volume.
<em>where P: is the gas pressure, T: is the gas temperature and k: is a constant.</em>
Therefore, due to Gay-Lussac's Law, when the plunger is pushed down very rapidly, the pressure of the air increase, which leads to its temperature increase. That is why cotton flashes and burns.
I hope it helps you!
Answer: 
Explanation:
According to Newton's 2nd Law of motion the force 
is proportional to the mass 
and acceleration 
:
(1)
On the other hand, the equation for the Centripetal force is:
(2)
Where:
is the velocity
is the radius of the circular motion
Making (1) and (2) equal:
(3)
Hence:
This is the expression for the centripetal acceleration
It should be noted, this acceleration is directed toward the center of the circumference of the circular motion (that's why it's called centripetal acceleration).
Answer:
c) 12
Explanation:
A Solar eclipse occurs when The Sun, The Earth and The Moon comes in a straight line with the Moon being in between the Earth and the Sun. At this point the Moon appears to block the Sun and Moon's shadow falls on Earth. This would occur only on the day of the New Moon.
If the Moon's orbit was in the same plane as that of the Earth's orbit. Every new Moon, there would be a Solar Eclipse. The Lunar cycle is of 29.5 Days which means there will be one new Moon every month. So there will be 12 Solar Eclipses every year.
Currently, the orbit of the Moon is tilted at an angle of 5° thus we don't see that many Solar eclipses. Maximum of 5 solar eclipses can occur in an year.
Let's calculate the average acceleration. It is the rate of changing speeds. Hence, we need to calculate the difference of speeds. 10-6=4 m/s. The rate is now
.
In general, the formula for the mean acceleration between two times 1 and 2 is given by:
where v1 and v2 are the speeds at the respective points and T is the time interval between them.
