Physics 101
		Exam 1 Solutions
		     2001

1) B  
      a = F/m.  In the first case a = 1 N/1 kg = 1 m/s^2
		In the 2nd   case a = 2 N/2 kg = 1 m/s^2

2) C
	a = delta v / t = 22 m/s / 0.1 s = 220 m/s^2

3) A
	This is the only statement that can be tested.  Go to the moon
	and try to eat some of it.

4) A
	By Newton's 1st law, there is no net force on the rock.
	Therefore it continues with the same velocity it had before
	(which is the velocity of the truck).

5) s = 10 km / 20 min = 0.5 km/min
     or
   s = 10 km / 20 min * (60 min/hr) = 30 km/hr
     both answers are acceptable

6) the speed is not changing.  Since the direction was not specified,
   we will ignore it.  Therefore, since the velocity is not changing,
   the accleration is zero.

7) C
   the change in velocity = a * t = 10 m/s^s downward * 1 s 
                                  = 10 m/s downward
   the new velocity = 50 m/s up + 10 m/s down = 40 m/s up

8) d = 1/2 g t^2 = 1/2 * 10 m/s^2 * (2 s)^2 = 20 m

9) A
   Note that there are three different chunks of gold; one on each planet.
   
   Just as the same mass would weigh less on the moon, it takes more
   mass to have the same weight.

   In equations: weight W = mg so if you know the weight and you
   know the gravitational field, then m = W/g. Thus, it takes the most
   mass to have the same weight when gravity is weakest.

10) B
    weight is a force.  It is measured in newtons

11) The net force is 10 N north + 15 N south = 5 N south

12) C
    constant velocity -> zero acceleration -> zero net force
    therefore you have to apply a force to exactly offset the force of
    friction.  Therefore you will have to apply 10 N of force in the
    opposite direction of the frictional force.

13) A
    If you keep the same force but increase the mass, then the
    acceleration will decrease.  It will take more time because there
    is less acceleration.

14) D
    You have tripled the mass (it was 1000 kg, it is now 3000 kg), so
    the acceleration will be one third as large (since F=ma).  This
    means, since  delta v = at, that it will take three times longer
    to reach 60 mi/h.

15) E
    The action/reaction pair is 
	The force of the bowstring on the arrow
	The force of the arrow on the bowstring

16) C
    By Newton's 3rd Law, the force of the bug on the car = the force
    of the car on the bug.