Chapter 6, Problem 1PQ

In many textbook problems, we ignore certain complications such as friction and drag. The problems contain key words that indicate such a simplification is being used. For example, if a surface is described as “slippery,” it means that we can ignore friction. Look at the previous chapters’ problem sets. Find five uses of these key words and explain how to interpret each case.

To determine

The simplification of problems by using keywords.

Answer to Problem 1PQ

Some keywords that simplify the problem are constant speed, straight line motion, parabolic trajectory, etc.

Explanation of Solution

In most cases, friction and air drag are neglected unless and until mentioned. When it is given “constant speed along a straight line path”, it implies that the acceleration and the net force on the moving body is zero. Also if the motion is along a straight line, the distance and displacement are the same and hence the speed and velocity are same.

When mentioned “follows a parabolic trajectory”, it means that the object undergoes projectile motion with negligible air resistance. An object “subjected to constant acceleration suddenly” would mean that the change in acceleration can be considered instantaneous.

While blocks on ice are considered, frictional force is ignored because they are negligibly small.