Do Now warm-up prompt

Kinetic Energy - the energy an object possesses due to its motion

Why Does It Shrink?

Temperature and Volume for a Gas

Why does the balloon shrink when it enters the liquid nitrogen?

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B) Kinetic Energy

the energy an object possesses due to its motion

Hammer hitting a nail
Boxer punching a speed bag
Spinning windmill

Newton mistakenly believed that the kinetic energy of a moving body was directly related to its velocity.

Willem 's Gravesande Experiment

Willem's Gravesande Experiment

[ Flash ]

Émilie du Châtelet

Portrait of Émilie du Châtelet by Latour
  • Translates and creates a commentary on Newton's Principia

  • Helps to develop Conservation of Energy (KE)

Émilie du Châtelet - She Showed Them The Physics

KE, V have a ....

Direct Square Relationship

Equation

KE = (½)mv2

Relationships

KE/m

Direct

KE = (½)mv2

KE/v?

Direct Square

Graph of kinetic energy vs. velocity

Ex 1

Given

A 60.0-kg runner has 1920 joules of kinetic energy.
Find: her speed (V = ?)

↓

KE = (½)mv2

1920 J = (½)(60.0 kg)V2

1920 J = 30V2

64.0 = V2

V = 8.00 m/s

Summary — W, KE, PE

K.E. - equivalent to work needed to get an object to a certain speed or to stop it.

P.E. - Equivalent to work needed to get an object to where it is or into its present condition. (spring)

W = Fd = ΔPE

Work and potential energy diagram
Given

W = 40 J

↓

ΔPE = 40 J

Cartoon owl sitting on a book

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. Kinetic energy is the energy an object has because of its

2. A 60.0 kg runner has 1920 J of kinetic energy. What is her speed?

3. Newton thought kinetic energy was directly proportional to velocity. If an object's speed triples, its KE actually becomes

4. What is the kinetic energy of a 2.0 kg cart moving at 3.0 m/s?

5. A student does 40 J of work lifting a box straight up at constant speed. How much does the box's gravitational PE increase?