There are two factors that contribute to the total stopping distance for a traveling vehicle. These two factors are the perception-reaction distance and the braking distance. When an event occurs that requires an emergency stop, the vehicle continues to travel at its initial velocity while the driver reacts to the event. The distance traveled for this time is the perception-reaction distance. Secondly, the vehicle undergoes constant acceleration while the brakes are applied. The distance traveled for this time interval is the braking distance. Historically, engineers have used a perception-reaction time of 0.75 seconds, but they now assume a perception-reaction time of 1.0 seconds for the average driver. Part (a) A vehicle has an initial velocity of vo. The driver has a perception-reaction time of t. When the driver begins braking, the vehicle has an acceleration of magnitude a. Write an expression for the total stopping distance of the vehicle. Part (b) A vehicle has an initial velocity of vo when a tree falls on the roadway a distance xf in front of the vehicle. The driver has a perception- reaction time of t. When the driver begins braking, the vehicle has an acceleration of magnitude a. Write an expression for the velocity of the vehicle when it hits the tree. Part (c) A vehicle has an initial velocity of Vo = 31 m/s when a tree falls on the roadway xf = 81 m in front of the vehicle. When the driver begins braking, the vehicle has an acceleration of magnitude a = 6.8 m/s². The driver has a perception-reaction time of 0.75 s. Calculate the velocity of the vehicle when it hits the tree. Part (d) A vehicle has an initial velocity of Vo = 31 m/s when a tree falls on the roadway xf = 87 m in front of the vehicle. When the driver begins braking, the vehicle has an acceleration of magnitude a = 6.8 m/s². The driver has a perception-reaction time of 1.00 s. Calculate the velocity of the vehicle when it hits the tree.
Displacement, Velocity and Acceleration
In classical mechanics, kinematics deals with the motion of a particle. It deals only with the position, velocity, acceleration, and displacement of a particle. It has no concern about the source of motion.
Linear Displacement
The term "displacement" refers to when something shifts away from its original "location," and "linear" refers to a straight line. As a result, “Linear Displacement” can be described as the movement of an object in a straight line along a single axis, for example, from side to side or up and down. Non-contact sensors such as LVDTs and other linear location sensors can calculate linear displacement. Non-contact sensors such as LVDTs and other linear location sensors can calculate linear displacement. Linear displacement is usually measured in millimeters or inches and may be positive or negative.
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