Advertisements
Advertisements
Question
Different points in earth are at slightly different distances from the sun and hence experience different forces due to gravitation. For a rigid body, we know that if various forces act at various points in it, the resultant motion is as if a net force acts on the c.m. (centre of mass) causing translation and a net torque at the c.m. causing rotation around an axis through the c.m. For the earth-sun system (approximating the earth as a uniform density sphere).
Options
the torque is zero.
the torque causes the earth to spin.
the rigid body result is not applicable since the earth is not even approximately a rigid body.
the torque causes the earth to move around the sun.
Advertisements
Solution
The torque is zero.
Explanation:
As the earth is revolving around the sun in a circular motion due to gravitational attraction. The force of attraction will be of radial nature i.e., the angle between position vector r and force F is zero. So, torque = |τ| = |r × F| = rFsin0° = 0.
APPEARS IN
RELATED QUESTIONS
Choose the correct alternative:
Acceleration due to gravity increases/decreases with increasing depth. (assume the earth to be a sphere of uniform density).
State and explain Kepler's laws of planetary motion. Draw diagrams to illustrate these laws.
At noon, the sun and the earth pull the objects on the earth's surface in opposite directions. At midnight, the sun and the earth pull these objects in same direction. Is the weight of an object, as measured by a spring balance on the earth's surface, more at midnight as compared to its weight at noon?
A solid sphere of mass m and radius r is placed inside a hollow thin spherical shell of mass M and radius R as shown in the following figure . A particle of mass m' is placed on the line joining the two centres at a distance x from the point of contact of the sphere and the shell. Find the magnitude of the resultant gravitational force on this particle due to the sphere and the shell if (a) r < x < 2r, (b) 2r < x < 2R and (c) x > 2R.
A ball is thrown vertically upwards. It goes to a height 20 m and then returns to the ground. Taking acceleration due to gravity g to be 10 ms-2 , find :
the total time of journey of the ball .
Who stated the law of gravitation?
Why don't you feel the force of attraction between your friend sitting close to you and yourself?
Name and state the action and reaction in the following case:
Hammering a nail.
Explain why:
The atmosphere does not escape.
Explain the difference between g and G.
Show that gravity decreases at higher altitudes.
What do you mean by a gravitational constant?
Solve the following problem.
Find the gravitational force between the Sun and the Earth.
Given Mass of the Sun = 1.99 × 1030 kg
Mass of the Earth = 5.98 × 1024 kg
The average distance between the Earth and the Sun = 1.5 × 1011 m.
Solve the following problem.
Calculate the acceleration due to gravity at a height of 300 km from the surface of the Earth. (M = 5.98 × 1024 kg, R = 6400 km).
The gravitational force between two bodies is directly proportional to the product of the masses of those bodies and is ______ of the distance between them.
Particles of masses 2M, m and M are respectively at points A, B and C with AB = ½ (BC). m is much-much smaller than M and at time t = 0, they are all at rest (Figure). At subsequent times before any collision takes place ______.
Answer the following questions in reference to the figure below:
- Which relation is shown in the figure?
- What will happen if the mass of one of the objects is doubled?
The Superposition Principle states that the net gravitational force on an object is ______.
The gravitational force between two objects acts in which direction?
