Gravitation — Set 5
Physics · गुरुत्वाकर्षण · Questions 41–50 of 60
What is the SI unit of the universal gravitational constant G?
Correct Answer: D. N m^2 kg^-2
From F = Gm1m2/r^2, G must make the units consistent. In SI, it is N m^2 kg^-2. This unit is the same everywhere in physics problems.
The standard approximate value of acceleration due to gravity at Earth’s surface is?
Correct Answer: A. 9.8 m/s^2
Near Earth’s surface, free-fall acceleration is about 9.8 m/s^2. It is often rounded to 10 m/s^2 for quick estimates. It varies slightly with latitude and altitude.
Weight of a body is best described as?
Correct Answer: D. Gravitational force acting on the body
Weight is the gravitational pull exerted on a mass. It equals W = mg near Earth’s surface. Because g can change, weight can change from place to place.
Kepler’s first law states that planets move in?
Correct Answer: A. Ellipses with the Sun at one focus
Kepler’s first law describes the shape of planetary orbits. It says each planet moves in an ellipse with the Sun at one focus. This explains why planets are sometimes closer or farther from the Sun.
Kepler’s second law is also called the law of?
Correct Answer: B. Equal areas in equal times
Kepler’s second law states that the line joining planet and Sun sweeps equal areas in equal times. This means the planet moves faster when it is closer to the Sun. It reflects conservation of angular momentum.
Which statement about gravitational force between two ordinary masses is correct?
Correct Answer: B. It is always attractive
Gravity between positive masses is attractive. The force pulls the masses toward each other. This is a basic property used in celestial motion.
For a satellite in uniform circular orbit, the centripetal force needed for circular motion is provided by?
Correct Answer: A. Gravitational force
A satellite needs centripetal force to keep turning in a circle. Gravity supplies this inward force. That is why the satellite keeps orbiting instead of flying away.
For a satellite of mass m moving in a circular orbit of radius r around a planet of mass M, the correct condition is?
Correct Answer: D. GMm/r^2 = mv^2/r
Gravity provides the centripetal force in circular motion. So GMm/r^2 must equal mv^2/r. From this, v = sqrt(GM/r) follows directly.
In gravitational problems, the gravitational potential at infinity is usually taken as?
Correct Answer: B. Zero
Potential is defined relative to a reference level. In gravitation, infinity is chosen as the reference. So V(∞) is taken as zero for convenience.
Ignoring air resistance, a body dropped from rest near Earth accelerates downward with?
Correct Answer: D. Approximately g
In free fall, gravity is the only significant force. That produces acceleration approximately equal to g. The mass cancels out in mg/m.