When a roller coaster is at the top of a steep hill, its potential energy is maximum. When it hurdles down the slope and comes to the bottom, the potential energy reduces greatly. Hence we can say that the law of conservation of energy is not valid here since energy is destroyed. a) True b) False

A system of two objects has AKtot = 7 J and AUint = -4 J. Part A How much work is done by interaction forces? Express your answer in joules. IVE ΑΣΦ Wint = Submit Part B How much work is done by external forces? Express your answer in joules. V—| ΑΣΦ Wext= = Request Answer Submit Request Answer ? ? J J

1. A roller-coaster car with a mass of 1200 kg starts at rest from a point 20 m above the ground. At point B, it is 9 m above the ground. [Express your answers in kilojoules (kJ).] a. What is the initial potential energy of the car? b. What is the potential energy at point B? c. If the initial kinetic energy was zero and the work done against friction between the starting point and point B is 40 000 J (40 kJ), what is the kinetic energy of the car at point B 2. The time required for one complete cycle of a mass oscillating at the end of a spring is 0.80 s. What is the frequency of oscillation?

Which of the following statements are true? Select all correct.   Question 3 options:   If an object speeds up, then the total work done on the object was positive.   If an object moves at a constant speed, then the work done by each individual force is zero   A force must be parallel to the displacement to do any work.   If a force is perpendicular to displacement, it does zero work.   If a force has a component in the opposite direction of the displacement, it does positive work.   If an object doesn't move, then the work done by every individual force must be zero.