Math Problem Statement

An arrow is shot straight upward on the moon with an initial velocity of 58 m/s. Its height in meters after t seconds is given by s(t) = 58t - 0.83t^2. The questions are: 1. What is the velocity of the arrow after 10 seconds? 2. How long will it take for the arrow to return and hit the moon? 3. With what velocity will the arrow hit the moon?

Solution

The problem provides the height s(t)s(t) of an arrow shot straight up on the moon, given as:

s(t)=58t0.83t2s(t) = 58t - 0.83t^2

where s(t)s(t) is the height in meters at time tt seconds. Let's break down each question:

  1. Velocity of the arrow after 10 seconds:

    The velocity is the derivative of the height function s(t)s(t), so we first compute v(t)=dsdtv(t) = \frac{ds}{dt}.

    v(t)=ddt(58t0.83t2)=582(0.83)t=581.66tv(t) = \frac{d}{dt} \left( 58t - 0.83t^2 \right) = 58 - 2(0.83)t = 58 - 1.66t

    After 10 seconds:

    v(10)=581.66×10=5816.6=41.4m/sv(10) = 58 - 1.66 \times 10 = 58 - 16.6 = 41.4 \, \text{m/s}

  2. Time for the arrow to return and hit the moon:

    The arrow will return to the moon when its height s(t)=0s(t) = 0. Solve 58t0.83t2=058t - 0.83t^2 = 0.

    Factor the equation:

    t(580.83t)=0t(58 - 0.83t) = 0

    So, t=0t = 0 (initial launch) or 580.83t=058 - 0.83t = 0.

    Solving 58=0.83t58 = 0.83t:

    t=580.8369.88secondst = \frac{58}{0.83} \approx 69.88 \, \text{seconds}

  3. Velocity at the moment the arrow hits the moon:

    The velocity at the time the arrow returns is calculated using v(t)=581.66tv(t) = 58 - 1.66t at t=69.88t = 69.88:

    v(69.88)=581.66×69.8858116=58m/sv(69.88) = 58 - 1.66 \times 69.88 \approx 58 - 116 = -58 \, \text{m/s}

    The negative sign indicates the arrow is traveling downward, and its magnitude is 58 m/s.


If you need more details or have questions, feel free to ask!

Here are some related questions to expand understanding:

  1. What is the significance of the negative velocity when the arrow hits the moon?
  2. How does the quadratic term 0.83t20.83t^2 affect the motion of the arrow?
  3. How would the trajectory change if the initial velocity were different?
  4. How do air resistance and gravity on Earth differ from this scenario on the moon?
  5. What would the maximum height of the arrow be, and how can we calculate it?

Tip: The time to reach maximum height is when the velocity v(t)=0v(t) = 0.

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Math Problem Analysis

Mathematical Concepts

Calculus
Derivatives
Quadratic Equations
Kinematics

Formulas

Velocity as the derivative of position: v(t) = ds/dt
Quadratic equation s(t) = at^2 + bt + c
Solving quadratic equations to find roots

Theorems

Derivative of a function
Quadratic formula

Suitable Grade Level

Grades 10-12