One-D Motion, Again - Faculty

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Department of Natural Sciences
Clayton State University
February 18, 2014
Physics 2211 – Quiz 4
Name ______SOLUTION_______________________________
1. A Honda Civic travels in a straight line along a road. Its distance x from a stop sign
is given as a function of time t by the equation x(t)= α t2− β t3, where α =
1.52m/s2 and β = 4.75×10−2m/s3.
a.
V x , av 
b.
V x , av 
c.
Calculate the average velocity of the car for the time interval t = 0 to t1 = 1.93 s.
x f  xi
t f  ti

5.32 m  0
 2.76 m / s
1.93 s
Calculate the average velocity of the car for the time interval t = 0 to t2 = 4.05 s.
x f  xi
t f  ti

21.77 m  0
 5.38 m / s
4.05 s
Calculate the instantaneous velocities of the car at t1 = 1.93 s and t2 = 4.05 s.
V x  2t  3t 2
Vx (t  1.93 s)  5.34 m / s
Vx (t  4.05 s)  9.98 m / s
d.
a x , av 
Calculate the average acceleration of the car from t1 = 1.93 s to t2 = 4.05 s.
Vx f  Vx i
t f  ti
 2.19 m / s 2
e.
Calculate the instantaneous acceleration of the car at t1 = 1.93 s.
a x  2  6t  2.49 m / s 2
2. The figure shows the velocity of a solar-powered car as a function of time. The
driver accelerates from a stop sign, cruises for 20 s at a constant speed of 60 km/h,
and then brakes to come to a stop 40 s after leaving the stop sign.
a. Compute the average acceleration during the time interval t=0 to t=10s.
V x (0)  0
V x (t  10 s)  60 km / h  16.7 m / s
a x  1.67 m / s 2
b. What is the instantaneous acceleration at t=20s?
Zero

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