QOD 97 Explain what it means when an

QOD 97 Explain what it means when an object accelerates at a rate of 2 m/s 2? When an object accelerates at a rate of 2 m/s 2 it means that every second, the speed increases by 2 m/s.

4 -22 -14 QOD 97 1. Explain what it means when an object accelerates at a rate of 2 m/s 2? When an object accelerates at a rate of 2 m/s 2 it means that every second, the speed increases by 2 m/s. 2. What is the acceleration of a cheetah that is running a velocity of 28 m/s and slows down to 20 m/s after 10 seconds? (Write equation & show steps) a = v f – vi a = 20 m/s – 28 m/s = -. 8 m/s t 10 s a = - 0. 8 m/s 2

Go over answers to finding acceleration

Calculating Potential & Kinetic Energy Potential Energy – stored energy of an object due to its state or position Kinetic Energy – energy of a moving object Unit – Joules (J)

1 Joule of Energy … • the energy required to lift a small apple (with a mass of approximately 100 g) vertically through one meter of air. • the energy released when that same apple falls one meter to the ground. • the kinetic energy of a 50 kg human moving very slowly (0. 2 m/s).

(Gravitational) Potential Energy PE = mgh Mass(kg) x Gravity x Height(m) = ___ Joules (J) Acceleration due to Gravity = 9. 8 m/s 2

Ex: 1 A box that has a mass of 2. 5 kg is sitting on a shelf that is 2 meters high. What is the gravitational potential energy of the box? • Mass = 2. 5 kg • Gravity = 9. 8 m/s 2 • Height = 2 m PE = mgh PE = 2. 5 kg x 9. 8 m/s 2 x 2 m = PE = 49 Joules (J)

Ex: 2 A boy has a mass of 55 kg. He climbs 12 meters up a tree. What is his gravitational potential energy? 55 kg • Mass = ____ 9. 8 m/s 2 • Gravity = ____ 12 m • Height = _______ PE = mgh PE = 55 kg x 9. 8 m/s 2 x 12 m = PE = 6, 468 Joules

Ex: 3 Find the gravitational potential energy of a pencil sitting on the edge of a desk. The pencil is 0. 25 kg and the desk is 0. 78 m high. PE = mgh PE =. 25 kg x 9. 8 m/s 2 x . 78 m = PE = 1. 911 J

Ex: 3 - challenge Find the gravitational potential energy of a pencil sitting on the edge of a desk. The pencil is 25 g and the desk is 78 cm high. . 025 Convert 25 g to ____ kg . 78 Convert 78 cm to ____ m PE = mgh PE =. 025 kg x 9. 8 m/s 2 x . 78 m = PE = 0. 191 J

Kinetic Energy 2 KE = 0. 5 xmv 0. 5 x Mass(kg) x Velocity(m/s) 2 = ___ Joules

Ex 4: Determine the kinetic energy of a 55 kg woman running with a speed of 3. 87 m/s. KE = 0. 5 x mv 2 KE = 0. 5 x 55 x (3. 87) 2 KE = 0. 5 x 55 x 14. 97 KE = 411. 9 Joules

Ex 5: What is the kinetic energy of a cheetah with a mass of 72 kg running a speed of 29 m/s. KE = 0. 5 x mv 2 KE = 0. 5 x 72 x (29) 2 KE = 0. 5 x 72 x 841 KE = 30, 276 Joules

Ex 6: What is the kinetic energy of a pencil with a mass of 0. 25 kg thrown a speed of 10 m/s. KE = 0. 5 x mv 2 KE = 0. 5 x 0. 25 x (10) 2 KE = 0. 5 x 0. 25 x 100 KE = 12. 5 Joules

Practice WS

Ex 4: (Create your own problem!) 1. With your partner, write a word problem that tells the mass and height of your object/person. 2. Draw a simple diagram of your word problem. 3. Solve your problem to find the gravitational potential energy of your object/person, but don’t write down the answer! 4. Pass the problem to your neighbors to solve.

KE = ½ x mass x velocity

Take Pictures!! • With a partner… – Take 3 pictures of kinetic energy • At least 1 must include a person – Take 3 pictures of potential energy • At least 1 must include a person