Math Problem Statement

find where the object is speeding up and slowing down

Find where the object is speeding up and slowing down

Solution

The position function of the object is given as:

s(t)=45t2109t+22s(t) = 45t^2 - 109t + 22

To determine where the object is speeding up and slowing down, we need to analyze the velocity and acceleration of the object. Here's the process:

Step 1: Find the velocity function

The velocity is the first derivative of the position function with respect to time tt:

v(t)=ds(t)dt=ddt(45t2109t+22)v(t) = \frac{ds(t)}{dt} = \frac{d}{dt}(45t^2 - 109t + 22)

v(t)=90t109v(t) = 90t - 109

Step 2: Find the acceleration function

The acceleration is the derivative of the velocity function:

a(t)=dv(t)dt=ddt(90t109)a(t) = \frac{dv(t)}{dt} = \frac{d}{dt}(90t - 109)

a(t)=90a(t) = 90

Step 3: Analyze speeding up and slowing down

  • The object is speeding up when the velocity and acceleration have the same sign (either both positive or both negative).
  • The object is slowing down when the velocity and acceleration have opposite signs.

Since the acceleration a(t)=90a(t) = 90 is constant and positive, we only need to analyze the velocity function v(t)=90t109v(t) = 90t - 109.

  1. Set the velocity equal to zero to find when the object changes direction:

v(t)=090t109=0v(t) = 0 \quad \Rightarrow \quad 90t - 109 = 0 t=109901.211t = \frac{109}{90} \approx 1.211

Step 4: Interpret the results

  • For t<1.211t < 1.211, v(t)<0v(t) < 0 (the object is moving in the negative direction).
  • For t>1.211t > 1.211, v(t)>0v(t) > 0 (the object is moving in the positive direction).

Since the acceleration is always positive, the object is:

  • Slowing down when t<1.211t < 1.211 (because v(t)v(t) is negative and a(t)a(t) is positive).
  • Speeding up when t>1.211t > 1.211 (because v(t)v(t) is positive and a(t)a(t) is positive).

Conclusion:

  • The object is slowing down in the interval [0,1.211][0, 1.211].
  • The object is speeding up in the interval [1.211,5][1.211, 5].

Would you like more details on any part of this process?


Here are five related questions for further exploration:

  1. How would the analysis change if the acceleration was not constant?
  2. What is the object's velocity at t=0t = 0 and t=5t = 5?
  3. How far has the object traveled by t=5t = 5?
  4. What would happen if the position function had a cubic term?
  5. How would you find the maximum or minimum position of the object?

Tip: To better understand motion, always analyze both velocity and acceleration functions. Velocity tells you the direction and speed of motion, while acceleration reveals changes in that speed.

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Math Problem Analysis

Mathematical Concepts

Calculus
Kinematics
Derivatives
Velocity
Acceleration

Formulas

Position function: s(t) = 45t^2 - 109t + 22
Velocity: v(t) = ds(t)/dt = 90t - 109
Acceleration: a(t) = dv(t)/dt = 90

Theorems

The object is speeding up when velocity and acceleration have the same sign.
The object is slowing down when velocity and acceleration have opposite signs.

Suitable Grade Level

Grades 11-12, University