The assertion mad by the Newton's first law of motion that every body continues in its state of uniform motion in the absence of external force appears to be contradicted in everyday experience. Why ?

State and explain the Newton's First Law of Motion.

How does Newton's first law of motion leads to the definition of force?

State and explain Newton's Second Law of motion with the help of this law how can we measure force.

Different points in earth are at slightly different distancesfrom 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 rotation around an axis thorugh the C.M. For the earth-sun system (approximating the earth as a uniform density sphere)

A wheel in uniform motion about an axis passing through its centre and perpendicular to its plane is considered to be in mechanical (translational plus rotational equilibrium because no net external force or torque is required to sustain its motion. However, the particles that constitute the wheel do experience a centripetal acceleration directed towards the centre. How do you reconcile this fact with the wheel being in equilibrium? How would you set a half - wheel into uniform motion about an axis passing through the centre of mass of the wheel and perpendicular to its plane? Wil you require external forces to sustain the motion?

Newton's law of gravitation states that everybody exerts a gravitational force on every other body. If this is true, why for example two boys sitting in the examination hall do not move towards each other due to this force?

Two long straight, current-carrying conductors , PQ and XY, are held a constant distance apart as shown in the figure. The conductors carry the magnitude of current in the same direction . A plan view form above the conductors is shown in the figure. Use Newton's third law of motion to state the direction of the force on wire XY.