# Problems In Physics

## Excerpt From The Book

Rectilinear Uniform Motion

In solving the problems both in this section and in Secs 2 and 3, special attention should be paid to the general rules for compounding and resolving motion as well as to the vectorial nature of the principal kinematic quantities (velocity and acceleration).

Such problems are sometimes difficult to solve, especially in the case of curvilinear motion or the relative motion of two bodies (for example, the motion of a ball falling to the ground relative to that of a ball thrown vertically upwards).

These difficulties can only be obviated by considering the separate components of motion independently and using the rules for compounding and resolving vectors correctly.

Many difficulties can be overcome if a correct general approach is used to solve problems on the curvilinear motion.

Most of the solutions in Sec. 3 are intended to show how the correct resolution of motion into components can reduce a complicated problem on a curvilinear motion to a simple, familiar problem involving two independent rectilinear motions.

When considering a uniformly variable motion, it is necessary to use the true physical sense of the equations for the path and velocity of this motion correctly.

For instance, when solving problems on the motion of a body projected into the air, students frequently break the solution down into two independent stages,

considering first the uniformly retarded motion upwards until the body comes to rest and then the uniformly accelerated motion downwards from rest.

This method lords a comparatively simple solution when only one body is in motion, but can hardly be applied when the problem describes

the simultaneous motion of several bodies (for example, Problems 31 and 35 where two bodies thrown upwards one after the other meet in the air).

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