CONSERVATION OF ENERGY CONSERVATION OF ENERGY For an

CONSERVATION OF ENERGY

CONSERVATION OF ENERGY For an isolated system, energy can be transformed to different forms, but cannot be created or destroyed.

INTERESTING IDEA https: //www. youtube. com/watch? v=Ppla. BASQ_3 M

ISOLATED SYSTEM A system of objects from which no energy can escape and there are no outside influences What is the biggest isolated system? How can we change energy in an isolated system?

WORK-ENERGY THEOREM

ANALYZING WORK-ENERGY THEOREM What types of energy can we calculate?

Start from Work

KINETIC ENERGY

Start from Work

GRAVITATIONAL POTENTIAL ENERGY

EXAMPLE # 1 A basketball player shoots a ball at a speed of 10. 0 m/s. The ball leaves the player’s hand at a height of 1. 98 m and goes through a 10. 0 foot high hoop. Calculate the speed of the ball as it goes through the hoop if air friction is neglect able. Note: 1 inch = 2. 54 cm (Use energy)

EXAMPLE # 2 A physics student slides down a hill on a sled. The mass of the sled and the physics student is 70. 0 kg. The student has a speed of 10. 0 m/s at the bottom of the hill and slides a horizontal distance of 34. 0 m from the bottom of the hill. Calculate the coefficient of friction between the snow and the sled.

SPRING MOTION When a spring is stretched and let go, the force that is produced is a function of the stretch of the spring We call this a Restorative Force k – spring constant (N/m) x – displacement (m) Why would the negative sign be present?

DETERMINE THE SPRING CONSTANT

Start from Work

EXAMPLE A spring (k=20 N/m) is compressed 30 cm by a ball (m= 100 g) and fired upwards. How fast will the object be moving after it has a vertical displacement of 20 cm after it leaves the spring?

26. A 0. 20 kg mass is hung from a vertical spring of force constant 55 N/m. When the spring is released from its unstretched equilibrium position, the mass is allowed to fall. Use the conservation of energy to determine: a) the speed of the mass after it falls 1. 5 cm. b) the distance the mass will fall before reversing direction

EXAMPLE A 35 kg child is bouncing on a pogo stick, if the spring constant is 4945 N/m and it is compressed by 25 cm, how high will the child bounce?