Help is very much appreciated

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.

The difference between a red shift and a blue shift has to do with wavelength frequency. t or f

Acar drives toward the right over the top of a hill, as shown below. which arrow represents the centripetal acceleration? w x y z