A caris parked on a cliff overlooking the ocean on an incline that makesan angle
ID: 1664431 • Letter: A
Question
A caris parked on a cliff overlooking the ocean on an incline that makesan angle of 16.0° below the horizontal. The negligent driverleaves the car in neutral, and the emergency brakes are defective.The car rolls from rest down the incline with a constantacceleration of2.59 m/s2 for a distanceof 30.0 m to the edge of thecliff, which is 30.0 m above theocean. (a)Find the car's position relative to the base of the cliff when thecar lands in the ocean.m
(b) Find the length of time the car is in the air.
s (a)Find the car's position relative to the base of the cliff when thecar lands in the ocean.
m
(b) Find the length of time the car is in the air.
s
Explanation / Answer
(a) the formula for horizontal displacement in projectile motionis x = v_0 cos(_0) * t here, we first need to find v_0, then we need to find t t is set by the constraint: when the car hits the ocean, the flightis over thus we will find t in (b) and then use it in (a) before we can do (b) we need to know at what velocity the cardeparts from the edge of the cliff; in some other problems that would ne unnecessary, but here welaunch with a velocity at an angle 16 degree below the horizontal therefore, the initial launch velocity has a horizontal AND avertical component and the vertical component is acting as a v_0 in the free fallwhich sets the time constraint for the total motion so ... first, calculate how fast a car gets which starts to roll from restfrom 30m away from the cliff use x= 30 = 1/2 a*t^2 to find the time for this first motion, whichwill determine the v_0 for the second motion second, use that t in v = a*t to determine the cars velocity whenit will have moved the 30m to the edge of th ecliff third: now analyze the triangle which is built by the angle 16degree below the horizontal and the velocity v from the first calculation as the hypotenuse; find thelengths of the two other sides of the triangle - they are the v_0x and v_0y for thefollowing projectile motion fourth, do the free fall for y = 30m = v_y0*t - 1/2 g t^2 to find the new time, th etime of the flight in the air fifth, use that time together with the v_0x in the very firstequation at the top to determine how far from the cliff the car hits the water :o)
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