Answer:
<em>The car will be moving at 5.48 m/s at the bottom of the hill</em>
Explanation:
<u>Principle of Conservation of Mechanical Energy</u>
In the absence of friction, the total mechanical energy is conserved. That means that
is constant, being U the potential energy and K the kinetic energy
U=mgh
When the car is at the top of the hill, its speed is 0, but its height h should be enough to produce the needed speed v down the hill.
The Kinetic energy is then, zero. When the car gets enough speed we assume it is achieved at ground level, so the potential energy runs out to zero but the Kinetic is at max. So the initial potential energy is transformed into kinetic energy.
We are given the initial potential energy U=45 J. It all is transformed to kinetic energy at the bottom of the hill, thus:
Multiplying by 2:
Dividing by m:
Taking square roots:
v = 5.48 m/s
The car will be moving at 5.48 m/s at the bottom of the hill
Let T1 and T2 be tension in ropes1 and 2 respectively.
<span>since system is stationary (equilibrium), considering both ropes + beam as a system </span>
<span>for horizontal equilibrium (no movement in that direction, so resultant force must be zero horizontally) </span>
<span>T1sin(20) = T2sin(30) </span>
<span>=> T1 = T2sin(30) / sin(20) </span>
<span>for vertical equilibrium, (no movement in this direction, so resultant force must be zero vertically) </span>
<span>T1cos(20) + T2cos(30) = mg </span>
<span>m = 900kg, substituting for T1 </span>
<span>T2sin(30)*cos(20)/sin(20) + T2cos(30) = 900g </span>
<span>2.328*T2 = 900*9.8 </span>
<span>T2 = 3788.65N </span>
<span>so T1 from (1) </span>
<span>T1 = 5535.21N</span>
Let's assume that ground level is the height 0 meters. The change in potential energy is going to be gravitational potential energy, which is given by PE=mgh.
ΔPE=mgh-mgy
=mg(h-y)
=50(28-0)
=1400 J
When we look at the moon from the Earth, we always see the same light spots, dark spots, and shapes. It never changes. There could be two possible reasons for this:
-- The moon is a flat disk with some markings on it, and one side of it always faces the Earth.
-- The moon is a round ball with some markings on it, and one side of it always faces the Earth.
Either way, since the same side always faces the Earth, the only way that can happen is if the moon's revolution around the Earth and rotation on its axis both take EXACTLY the same length of time.
Even if they were only one second different, then we would see the moon's whole surface over a long period of time. But we don't. So the moon's rotation and revolution must be EXACTLY locked to the same period of time.
The answer id D Has a very fast-growing economy.
Have a nice day
