27. A driver of a car going 25.0 m/s suddenly notices a stop sign 40.0 m ahead. The braking deceleration rate of the car is 10.0 m/s², but it takes the driver 0.75 s (reaction time) to get the brakes applied. (a) Determine if the car runs the stop sign. (b) Determine the maximum initial speed at which the car could be moving and manage to stop at the sign.

As a city planner, you receive complaints from local residents about the safety of nearby roads and streets. One complaint concerns a stop sign at the corner of Pine Street and 1st Street. Residents complain that the speed limit in the area (55 mph) is too high to allow vehicles to stop in time. Under normal conditions this is not a problem, but when fog rolls in visibility can reduce to only 155 ft. Since fog is a common occurrence in this region, you decide to investigate. The state highway department states that the effective coefficient of friction between a rolling wheel and asphalt ranges between 0.689 and 0.770, whereas the effective coefficient of friction between a skidding (locked) wheel and asphalt ranges between 0.450 and 0.617. Vehicles of all types travel on the road, from small VW bugs weighing 1210 lb to large trucks weighing 8640 lb. Considering that some drivers will brake properly when slowing down and others will skid to stop, calculate the minimum and maximum…

A car starts from rest, then accelerates at 1.20 m/s? for 7.00 s. It hits the brakes, slowing to a stop at a rate of -4.25 m/s². What is the total time for the problem? (Unit = s)

The height of a helicopter above the ground is given by h = 3t^2+2.0t^4, where h is in meters and t is in seconds. At t=2.0s, the helicopter releases a small bag. a) Calculate the maximum height the bag reaches measured from the ground. b) How long after the bad is released, does it strike the ground? c) Calculate the speed of vag when it hits the ground.