Math Problem Statement

A particle moves along the y-axis such that its position at time t is given by y(t) = 2t3 − 3t2 for t ≥ 0. At what time is the particle speeding up? (10 points)

Solution

To determine when the particle is speeding up, we need to evaluate the velocity v(t)v(t) and acceleration a(t)a(t) of the particle and find where their signs are the same (both positive or both negative). Here's the step-by-step process:

Step 1: Find the velocity v(t)v(t)

The velocity is the derivative of the position function y(t)y(t): v(t)=dydt=ddt(2t33t2)=6t26tv(t) = \frac{dy}{dt} = \frac{d}{dt}(2t^3 - 3t^2) = 6t^2 - 6t v(t)=6t(t1)v(t) = 6t(t - 1)

Step 2: Find the acceleration a(t)a(t)

The acceleration is the derivative of the velocity function v(t)v(t): a(t)=dvdt=ddt(6t26t)=12t6a(t) = \frac{dv}{dt} = \frac{d}{dt}(6t^2 - 6t) = 12t - 6

Step 3: Analyze the velocity and acceleration signs

  • Velocity v(t)=6t(t1)v(t) = 6t(t - 1):

    • v(t)=0v(t) = 0 when t=0t = 0 or t=1t = 1.
    • The sign of v(t)v(t) depends on the intervals:
      • For t(0,1)t \in (0, 1), v(t)<0v(t) < 0.
      • For t>1t > 1, v(t)>0v(t) > 0.
  • Acceleration a(t)=12t6a(t) = 12t - 6:

    • a(t)=0a(t) = 0 when t=0.5t = 0.5.
    • The sign of a(t)a(t) depends on the intervals:
      • For t<0.5t < 0.5, a(t)<0a(t) < 0.
      • For t>0.5t > 0.5, a(t)>0a(t) > 0.

Step 4: Determine when the particle is speeding up

The particle is speeding up when both velocity v(t)v(t) and acceleration a(t)a(t) have the same sign:

  1. For t(0,0.5)t \in (0, 0.5):

    • v(t)<0v(t) < 0 and a(t)<0a(t) < 0 → Speeding up.
  2. For t(1,)t \in (1, \infty):

    • v(t)>0v(t) > 0 and a(t)>0a(t) > 0 → Speeding up.

Final Answer:

The particle is speeding up for: t(0,0.5)(1,)t \in (0, 0.5) \cup (1, \infty)


Would you like further details or clarification?
Here are 5 related questions for practice:

  1. How do you determine when a particle is slowing down?
  2. What is the particle's position at t=2t = 2?
  3. Can a particle have zero velocity but nonzero acceleration?
  4. What are the intervals when the particle is moving downward?
  5. How would you graph v(t)v(t) and a(t)a(t)?

Tip: Always check the signs of velocity and acceleration to determine motion characteristics like speeding up or slowing down!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Velocity and Acceleration
Motion Analysis

Formulas

v(t) = dy/dt
a(t) = dv/dt
Speeding up when v(t) and a(t) have the same sign

Theorems

Sign Analysis for Velocity and Acceleration

Suitable Grade Level

Grades 11-12