Answers to even problems, Quiz 1 and 2: Chapter 2
CQ (conceptual question) 6. (a) B  (b) D (c) A, C and E (d) D
6. 
(a) between  0 and 1 seconds, velocity = 0; 1 and 3 seconds, velocity is positive,  constant at 5 m/s; 3 and 4 seconds, velocity is negative, constant at -20 m/s.  Get these  values using the rise/run formula for slopes. 
(b) Turning point at 3  s.
8. Between  0 and 2 seconds, acceleration = 0; 2 and 4 seconds, acceleration is positive and constant at 1 m/s2. Find these  values using  rise/run  for slopes. 
10. (a) 6 m  (b) 4 m/s (c) 2 m/s2
12. 
(a) 8.75 m/s2  
(b) Acceleration a  is approximately g = 9.8 m/s2 . This is reasonable. A person in their seat will feel a backward force of magnitude ma, where m is the passenger's mass and a the plane's acceleration.  This is a pseudo force. Resulting from  the passenger being in an accelerated reference frame, it's  not real. 

According to  someone watching from an inertial (non-accelerated) frame in the  airport, the passenger wants to remain at rest whereas the plane is accelerating forward.  That person sees the seat press forward into the  passenger's back. 

The passenger who feels  pressure from the forward accelerating seat has a different explanation.  In her non-inertial (accelerated) frame, she might think a long range gravitational force, perhaps from a black hole behind the idling plane,  is selectively pulling her backward into the seat before take off.  (We assume the windows are covered and her ears plugged to encourage the impression the plane is at rest.)   For further information, see fig 5.22.   

Albert Einstein asserted that the gravitational force she would experience locally while standing near a massive body (such as a Black Hole)  is actually the same as the pseudo-force experienced by her in the non-inertial (accelerated) frame of reference. This is called the Principle of Equivalence. Check out this link for more info: http://en.wikipedia.org/wiki/Equivalence_principle .
16. 

(a) make a table 


time(s)

Vx  (m/s)

Y(m) (Launch point  at y = 0)
1 9.8 14.7
2 0 19.6
3 -9.8 14.7
4 -19.6 0
(b) Velocity vs t  is a straight line with  negative slope = -g.  
50. (a)  27 m/s2. (b) 400 m/s. 
66. (a) 900 m  (b) 60 m/s