1.
10902-Physics 1A
                                             Physics Division
Tutorial 6 Solutions for Exercises
4.     (a) What is the momentum of a garbage truck that is 1.20 104 kg and is moving at
       10.0 m/s ? (b) At what speed would an 8.00-kg trash can have the same momentum as
       the truck?
Solution:
       (a) p  mv  1.20  104 kg 30.0 m/s  3.60  105 kg  m/s
                             p 3.60  105 kg  m/s
       (b) p  mv  v                             4.50  104 m/s
                             m      8.00 kg
5.     A bullet is accelerated down the barrel of a gun by hot gases produced in the combustion
       of gun powder. What is the average force exerted on a 0.0300-kg bullet to accelerate it
       to a speed of 600 m/s in a time of 2.00 ms (milliseconds)?
Solution:
                  p mv 0.0300 kg  600 m/s
        net F                              9.00  103 N
                  t   t   2.00  103 s
6.     Train cars are coupled together by being bumped into one another. Suppose two loaded
       train cars are moving toward one another, the first having a mass of 150,000 kg and a
       velocity of 0.300 m/s, and the second having a mass of 110,000 kg and a velocity of
         0.120 m/s . (The minus indicates direction of motion.) What is their final velocity?
Solution:
        m1v1  m2 v2  (m1  m2 )v' ,
            m v  m2 v2 150,000kg 0.300 m/s  110,000kg  0.120 m/s
        v'  1 1                                                            0.122 m/s
              m1  m2                 150,000kg  110,000kg
7.      Two manned satellites approach one another at a relative speed of 0.250 m/s, intending
       to dock. The first has a mass of 4.00  103 kg , and the second a mass of 7.50 103 kg . If
       the two satellites collide elastically rather than dock, what is their final relative velocity?
Solution:
       In a one-dimensional elastic collision of two objects, the momentum and kinetic
       energies before and after the collision are conserved:
                                                      2           2     2
        m1 (v1  v1' )  m2 (v2'  v2 ) and m1 (v1  v1 )  m2 ( v 2  v1 )
                                                 2    '           '
       Solving the two equations gives the result: v1  v2  (v1'  v'2 )
       So, the relative velocity of approach equals the relative velocity of recession = 0.25 m/s
Answers Only to Chapter 8 [Linear momentum]-Highlighted in Course Outline
2. (a) 1.20 x 108 kg, (b) 1.21 x 103
4. Exercise Question #4
6. 1.78 x 1029 kg·m/s
7. Exercise Question #5
9. (a) 2.40 x 103 N, (b) force same but in opposite direction.
12. F = 6.67 x 106 N
17. 2.10 x 103 N
23. Exercise Question #6
24. v = 0.272 m/s
27. v = 22.4 m/s
29. Exercise Question #7
30. Vgoalie = 0.150 m/s, Vpuck = -34.9 m/s
32. (a) V = 1.78 /s (b) -267 J
36. (a) V = 0.182 m/s, (b) 8.52 x 103 J
42. V = 24.8 m/s
43. V= 1.07 m/s