1. Warm-up Turn in Work Practice
A 180 g crate is raised 11.0 m above a platform by a fork lift. How much work is done on the crate?

2. Kinetic Energy

3. What is Energy? Energy is the ability to cause change
Energy can change the object itself, or its surroundings
Energy is measured in Joules

4. Forms of Energy
Some forms of energy are electrical, chemical, radiant, thermal, and mechanical
Energy can change between these forms

5. Kinetic Energy
Kinetic Energy: the energy of an object that is due to the object’s motion.
𝐾𝐸= 1 2 𝑚 𝑣 2
𝑘𝑖𝑛𝑒𝑡𝑖𝑐 𝑒𝑛𝑒𝑟𝑔𝑦= 1 2 𝑥 𝑚𝑎𝑠𝑠 𝑥 (𝑠𝑝𝑒𝑒𝑑) 2
Scalar Quantity
The SI unit for kinetic energy (and all other forms of energy) is the Joules, J
Mass must be in kg and speed must be in m/s

6. Practice 1
A cheetah can run briefly with a speed of 31.0 m/s. Suppose a cheetah with a mass of 47.0 kg runs at this speed. What is the cheetah’s kinetic energy?

7. Practice 2
A 7.00 kg bowling ball moves at 3.00 m/s. How fast must a g table-tennis ball move in order to have the same kinetic energy as the bowling ball?

8. Practice 2
𝒗 𝒕 =𝟏.𝟔𝟎 𝒙 𝟏𝟎 𝟐 𝒎/𝒔 Is this speed reasonable for a table-tennis ball in play? This speed would be very fast for a table-tennis ball

9. Work-Kinetic Energy Theorem
Work-Kinetic Energy Theorem states that the net work done by all the forces acting on an object is equal to the change in the object’s kinetic energy.
𝑊 𝑛𝑒𝑡 =∆𝐾𝐸

10. Practice 3
On a frozen pond, a person kicks a 10.0 kg sled, giving it an initial speed of 2.2 m/s. How far does the sled move if the coefficient of kinetic friction between the sled and the ice is 0.10? Remember: 𝐹 𝑘,𝑓 = 𝜇 𝑘 𝐹 𝑁

11. Warm-up
What is the relationship between the mass of an object and its KE?
What is the relationship between the speed of an object and its KE?
Reminders
Test Corrections Due Wednesday 2/20 at the end of lunch