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Kinetic Energy

L20: Mahi Tuatahi (2016 Exam)

Te Whakatika

A horse has four hooves, so the total surface area that the horse is exerting pressure through is $A = 0.0044 \times 4 = 0.0176m^{2}$

\begin{aligned} P &= \frac{F}{A} \
200155 &= \frac{F}{0.0176} \
200155 \times 0.0176 &= F = 3522.728N \end{aligned}

Ngā Whāinga Ako

  1. Give the symbols and units for kinetic energy
  2. $E_{k} = \frac{1}{2}mv^{2}$

:::instruction Write the date, the learning outcomes and title “Kinetic Energy” in your books. :::

Kinetic Energy

What is Kinetic Energy?

Kinetic energy is the energy that an object possesses due to its velocity!

Calculating Kinetic Energy

Kinetic energy depends on the mass and velocity of an object.

\begin{aligned} E_{k} &= \frac{1}{2} \times mass \times \text{velocity squared} \
E_{k} &= \frac{1}{2} \times m \times v^{2} \end{aligned}

What does $v^{2}$ mean?

\begin{aligned} & E_{k} = \frac{1}{2} \times m \times v \times v \end{aligned}

Pātai Tahi

Mr LeSueur rides his bike to work at $32km/h$ ($8.89ms^{-1}$). Both he and his bike have a combined mass of $80kg$. Calculate his kinetic energy.

Whakatika Tahi

We know $m=80kg$ and $v=8.89ms^{-1}$, and we are looking for $E_{k}$.

\begin{aligned} E_{k} = \frac{1}{2} \times 80 \times 8.89^{2} \
E_{k} = 3161.284J \end{aligned}

Pātai Rua

Sophie is skiing down Upper Fascination at Mt Hutt, and is trying to go really fast. Her combined mass is $60kg$ and she is moving at $60km/h$ ($16.67ms^{-1}$). Calculate her kinetic energy.

Whakatika Tua

We know $m=60kg$ and $v=16.67ms^{-1}$, and we are looking for $E_{k}$.

\begin{aligned} E_{k} = \frac{1}{2} \times 60 \times 16.67^{2} \
E_{k} = 8336.667J \end{aligned}

Whakamātau: Finding Your Kinetic Energy

Open the whakamātau document on Google Classroom!

Extra Work