An object is placed 13 cm from a concave spherical mirror of radius 9.0 cm. What type of image forms, and at what distance from the mirror? A. virtual image, 6.9 cm from the mirror
B. real image, 6.9 cm from the mirror
C. real image, 29 cm from the mirror
D. virtual image, 4.0 cm from the mirror

20. threshold braking in the vehicle's braking system occurs when a. the brake pedal is pushed, heel on floorboard, with full foot pressure. b. the brakes are exerting full braking power, without traction loss. c. the driver begins pushing down the brake pedal, with moderate slowdown. d. the brakes just begin to take hold with a gradual slowdown.

Two polarizers are oriented at 40∘ to each other and plane-polarized light is incident on them. if only 16 percent of the light gets through both of them, what was the initial polarization direction of the incident light?

Considering only the earth's rotation, determine how much later the asteroid would have had to arrive to put the explosion above helsinki at longitude 25˚ e? this would have obliterated the city.