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The TNB Frame

The unit tangent, normal and binormal vectors as a moving frame recording direction of travel, direction of turning and axis of rotation along a curve.

Active Calculus Multivariable, The TNB Frame

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3 exercises

Activity 10.5.4

In general, calculating N⃗\vN as a function of the parameter tt ends up being very difficult because there are multiple compositions of functions involved which means there is a nesting of chain rules involved in the definition. In this activity, we will examine how to go through the direct calculation of N⃗\vN for a curve parameterized by r⃗(t)=⟨t,t2,t3⟩\vr(t) =\langle t,t^2,t^3\rangle.

  1. Calculate velocity v⃗(t)\vv(t) and speed(t)\text{speed}(t) for the parameterization r⃗(t)=⟨t,t2,t3⟩\vr(t) =\langle t,t^2,t^3\rangle.

  2. Now calcula…

2.5

Activity 10.5.5

  1. Each race car has a 1 meter arrow attached to the hood of the car which points straight ahead. This arrow will measure the three dimensional vector that is the direction of travel. Is the direction of travel a property of the driver or the road? Be sure to explain your answer.

  2. The turn signal is measured by checking to see if the steering wheel is turned left or right. We are not measuring how much…

2.5

Exercise 9

Consider the moving particle whose position at time tt in seconds is given by the vector-valued function r⃗\vr defined by r⃗(t)=5tı^+4sin⁡(3t)ȷ^+4cos⁡(3t)k^\vr(t) = 5t \vi + 4\sin(3t) \vj + 4\cos(3t) \vk. Use this function to answer each of the following questions.

  1. Find the unit tangent vector, T⃗(t)\vT(t), to the space curve traced by r⃗(t)\vr(t) at time tt. Write one sentence that explains what T⃗(t)\vT(t) tells us about the particle's motion.

  2. Determine the speed of the particle moving along the space curve wit…

2.5

Adapted from Active Calculus Multivariable © 2013–2026 Nicholas Long, Mitchel T. Keller, and Steven Schlicker. Licensed under CC BY-SA 4.0. Source: Active Calculus Multivariable. Imported at revision 692c03c.