PHYS 2110, General Physics I North Carolina Central University Department of Phy

Question

PHYS 2110, General Physics I North Carolina Central University Department of Physics Test I - Spring 2016 A motorist travels 160 km at 80 km/h and 240 km at 100 km/h. What is the average speed of the motorist for this trip? A ball is thrown downward from the top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0 s. How high is the building? (neglect air resistance) A car starting from rest and accelerates constantly at 4.0 m/s^2 for 5.0 s in the x-direction, then travels with constant velocity for another 10 s, and finally decelerates constantly at the rate of 2.0 m/s^2 for 4.0 s. What is the car's final speed? An airplane travels at 450 mi/h east for 2.0 h and then at 250 mi/h west for 3 h. What is the average velocity for the trip? In the graph shown below what is the acceleration between 2 and 4.0 s Using the same graph in the above problem, what is the distance traveled from 4 to 6 s? Please find the total displacement (magnitude and direction) for vectors below.

Explanation / Answer

part 13 )

t1 = 160/80 = 3 hr

t2 = 240/100 = 2.4 r

average speed = total distance /total time

average speed = (160 + 240) / ( 3 + 2.4) = 74.07 km/h

part 16 )

y = ut + at^2/2

y = 25 *2 + 9.9 * 2^2 /2

y = 69.6 m

part 17 )

speed in 5 s

starting from rest u = 0

v = at = 5 * 4 = 20 m/s

now it moves contant velocity so a = 0

it start deccelerate

v = u - at

v = 20 - 2 * 4

v = 12 m/s

part 18 )

vavg = displacement/time

vavg = 900 - 750 / 5

vavg = 30 mi/h

part 19 )

a = dv/dt = 0

part 20 )

distance is the area of the curve ov v and t

d = 1/2 * 2 * 20 = 20

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