A disk is spinning about its center with a constant angular speed at first. Let the turntable spin faster and faster, with const
ant angular acceleration ?. Which sketch qualitatively shows the direction of the acceleration vector a of the bug?
1 answer:
Answer:
4 (please see the attached file)
Explanation:
While the angular speed (counterclockwise) remained constant, the angular acceleration was just zero.
So, the only force acting on the bug (parallel to the surface) was the centripetal force, producing a centripetal acceleration directed towards the center of the disk.
When the turntable started to spin faster and faster, this caused a change in the angular speed, represented by the appearance of an angular acceleration α.
This acceleration is related with the tangential acceleration, by this expression:
at = α*r
This acceleration, tangent to the disk (aiming in the same direction of the movement, which is counterclockwise, as showed in the pictures) adds vectorially with the centripetal force, giving a resultant like the one showed in the sketch Nº 4.
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Answer:
The rotational speed of the four smallest planets can be determined using the rotational speeds of the four largest planets and their orbital periods.
Explanation:
Kepler's three laws are:
1) The orbits of the planets around the Sun are ellipses, with the Sun at one of the focii
2) A line connecting the Sun with each planet sweeps out equal areas in equal time intervals
3) The cube of the semi-major axis of the orbit of one planet is proportional to the square of its orbital period
There 3 laws help explaining the following statements:
- <em>A planet's distance from the sun will not be the same in six months. --> </em>using the 1st law. In fact, since the orbit is an ellipse (and not a circle), and the Sun is at one of the focii, the distance of the planet from the Sun keeps changing during the year.
-<em> A planet's speed as it moves around the sun will not be the same in six months. -</em>-> using the 2nd law. In fact, since the line connecting the Sun to the planet must cover equal areas in the same time interval, it follows that the speed of the planet cannot be constant during the year (it will be faster when closer to the sun and slower when far from the sun).
- <em>The average distance of Saturn can be calculated using the average distance of Neptune and the orbital period of both planets. </em>--> using the 3rd law. In fact, the ratio (where a is the semi-major axis of the orbit and T the orbital period) is constant and it is the same for every planet orbiting the sun, so by knowing the data of Neptune and the orbital period of Saturn, it is possible to calculate Saturn's average distance.
Instead, the following statement:
<em>The rotational speed of the four smallest planets can be determined using the rotational speeds of the four largest planets and their orbital periods.</em>
Is not supported by any Kepler's law.
Answer:
Change in kinetic energy is ( 26CL³)/3
Explanation:
Given :
Net force applied, F(x) = Cx² ....(1)
Displacement of the particle from xi = L to xf = 3L.
The work-energy theorem states that change in kinetic energy of the particle is equal to the net amount of work is done to displace the particle.
That is,
ΔK = W = ∫F·dx
Substitute equation (1) in the above equation.
ΔK = ∫Cx²dx
The limit of integration from xi = L to xf = 3L, so
Substitute the values of xi and xf in the above equation.
Given :
Initial velocity, u = -6 m/s.
Time taken, t = 4 seconds.
Acceleration due to gravity, .( Here negative sign means downward direction )
To Find :
Velocity after 4 seconds.
Solution :
By equation of motion.
v = u + at
Here , a = g.
v = u + gt
v = -6 + (-9.8)×4
v = -6 + (-39.2)
v = -45.2 m/s
Therefore, velocity after 4 seconds is -45.2 m/s.
Hence, this is the required solution.