Activity 3.6.1. The Tortoise and the Pebble.
A tortoise is walking across the desert floor when it encounters a small pebble that it wants to climb over. It uses one of its front legs to act a normal force with magnitude \(F^N\) on the pebble, causing the pebble to act a normal force with magnitude \(F^N\) on the tortoise.
(a) Choosing a Reference Frame.
Two potential reference frames, both stationary with respect to the ground, are shown in the figure. Before doing any calculations: which reference frame do you think would be easier to use for describing the normal force on the tortoise by the pebble?
(b) Represent.
Sketch a diagram showing the normal force on the tortoise by the pebble in each reference frame. Make sure to include the components of the force and the given angle \(\theta\text{.}\)
(c) Key Skill: Breaking a Vector into Components.
For both reference frames, determine the \(x\) and \(y\) components of the normal force on the tortoise by the pebble.
(d) Metacognition.
Revisit your answer to the first part of the activity. Which reference frame do you think ended up being easier to describe the normal force? Why?
