Question 1: A planet is moving in an elliptical orbit. If T, V, E and L are respectively the kinetic energy, potential energy, total energy and the magnitude of the angular momentum of the planet then the true statement out of the following is:
Answer: (c) E is always negative
Question 2: The gravitational field in a region is given by N/kg then the magnitude of the gravitational force acting on a particle of mass 2 kg placed at the orgin, will be:
Answer: (c)26 N
Explanation: Given
Its magnitude
Thus,
= 13 × 2
= 26 N
Question 3: The minimum energy required to launch a m kg satellite from earth's surface in a circular orbit at an altitude of 2R where R is the radius of earth, will be:
Answer: (b)
Question 4: The gravitational potential difference between the surface of a planet and a point 20 m above it is 16 J/kg. Then the work done in moving a 2 kg mass by 8 m on a slope 60º from the horizontal, is:
Answer: (a) 11.1 J
Question 5: Three particles, each of mass 10_2 kg are brought from infinity to the vertices of an equilateral triangle of side 0.1 m, the work done is:
Answer: (d) 2 × 10–13 J
Explanation: The work done in bringing each mass m from infinity to the vertices of equilateral triangle of side r is negative of the gravitational potential energy of the system.
W = – U
= 2 × 10–13 J
Copyright © excellup 2014