01.(4 pts] The International Space Station orbits the Earth every 91 minutes at
ID: 1770345 • Letter: 0
Question
01.(4 pts] The International Space Station orbits the Earth every 91 minutes at a distance of 353 km above the surface of the Earth. The astronauts and their equipment are clearly weightless. Why is this? [A] They are further from the Earth, and the force of gravity is diminished almost to zero. [B] Objects in space have no mass, hence no gravitational attraction. [C] They are in vacuum where gravity does not operate. [D] They are in free fall. Q2. [4 pts] If the radius of the Earth was twice as large as it is, its gravitational pull would be: A] twice what it is now [B] four times what it is now C] one half of what it is now [D] one quarter of what it is now [E] the same as it is now Q3. [4 pts] When a mass goes in a horizontal circle with speed V at the end of a string of length L on a frictionless table, the tension in the string is T. If the speed of this mass were quadrupled, but all else remained the same, the tension would be [A] T/4 [B] 4T [C] 16T D] T 04. [4 pts] An object moves in a circular path at a constant speed. What is the direction of the net force acting on the object? [A] The net force is zero because the object is moving with a constant speed. [B] The net force points in the direction opposite to the motion of the object. [C] The net force is directed away from the center of the circular path. D] The net force is directed toward the center of the circular path. [E] The net force points in the same direction as the motion of the object. Q5. [4 pts] Two marbles, one twice as heavy as the other, are dropped to the ground from the roof of a building. Just before hitting the ground, the heavier marble is moving at [A] the same speed as the lighter one. [B] twice the speed of the lighter one. [C] half the speed of the lighter one D] V2 times the speed of the lighter one.Explanation / Answer
1) Answer: D part
The Earth's gravity is only slightly weaker at the altitude of the ISS than at the surface, but objects in orbit are in a continuous state of freefall, resulting in an apparent state of weightlessness.
2) Answer: A part
3) Answer: C part
a = v^2 / L
T = m * a
T = v^2 * m / L
If you quadruple the velocity, tension would become 16 times the original.
a = acceleration, m = mass, v = velocity (speed), T = force (tension)
4) Answer: D part
The net force acting upon such an object is directed towards the center of the circle. The net force is said to be an inward or centripetal force. Without such an inward force, an object would continue in a straight line, never deviating from its direction. Yet, with the inward net force directed perpendicular to the velocity vector, the object is always changing its direction and undergoing an inward acceleration.
The direction is inward therefore the net force is zero.
5) Answer: A part
Objects in free fall (with no air resistance) have acceleration equal to g=9.8 m/s^2, so both marbles hit the ground with the same speed.
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