A stellar black hole may form when a massive star dies. The mass of the star collapses down to a single point. Imagine an astronaut orbiting a black hole having five times the mass of the Sun. Assume the orbit is circular. (a) Find the speed of the astronaut if his orbital radius is r = 1 AU. m/s (b) Find his speed if his orbital radius is r = 7.4 km. m/s (c) CHECK and THINK: Compare your answers to the speed of light in a vacuum. What would the astronaut's orbital speed be if his orbital radius were smaller than 7.4 km?Karen and Randy are playing with a toy car and track. They set up the track on the floor as shown in the figure below, where the apparatus on the far left is used to launch the car forward by pressing down on the top portion. After the car is launched, it follows the track and continues, leaving the track at an angle of 0 = 25.00 with respect to the floor, at a height of h = 0.38 m above the floor. If the car has a mass of 136 g and it leaves the track with a speed of v = 4.04 m/s, what is the maximum height reached by the car, relative to the floor? Use conservation of energy to solve this problem. Ignore the effects of friction and air resistance. m