Momentum Assignment B
1. A 0.105-kg hockey puck moving at 48 m/s is caught by a 75-kg goalie at
rest. With what velocity does the goalie slide on the ice after catching the
puck?
2. A 35.0-g bullet strikes a 5.0-kg stationary wooden block and embeds itself
in the block. The block and bullet move together at 8.6 m/s. What was the
original velocity of the bullet?
3. A 35.0-g bullet moving at 475 m/s strikes a 2.5-kg wooden block. The
bullet passes through the block, leaving at 275 m/s. The block was at rest
when it was hit. How fast is it moving when the bullet leaves?
4. A 0.50-kg ball traveling at 6.0 m/s collides head-on with a 1.00-kg ball
moving in the opposite direction at a velocity of -12.0 m/s. The 0.50-kg ball
moves away at -14 m/s after the collision. Find the velocity of the second
ball.
5. A 3000-kg truck moving rightward with a speed of 5 km/hr collides headon with a 1000-kg car moving leftward with a speed of 10 km/hr. The two
vehicles stick together and move with the same velocity after the collision.
Determine the post-collision velocity of the car and truck. (CAREFUL: Be
cautious of the +/- sign on the velocity of the two vehicles.)
6. During a goal-line stand, a 75-kg fullback moving eastward with a speed
of 8 m/s collides head-on with a 100-kg lineman moving westward with a
speed of 4 m/s. The two players collide and stick together, moving at the
same velocity after the collision. Determine the post-collision velocity of the
two players. (CAREFUL: Be cautious of the +/- sign on the velocity of the
two players.)
7. A van has five times the mass of a small car. If the van coasts at 10 km/hr
into the car that is initially at rest, how fast do the two coast if they attach
together?
8. Trigonometry challenge question:
Object A is moving due east, while object B is moving due north. They
collide and stick together in a completely inelastic collision. Momentum is
conserved. Object A has a mass of 16.6 kg and an initial velocity of 7.13 m/s
due east. Object B has a mass of 29.1 kg and an initial velocity of 5.28 m/s
due north. Find:
a) magnitude of the momentum after the collision
b) direction of the total momentum of this two-object system after the
collision.
Solutions
1. Momentumbefore
=
Momentumafter
(0.105 kg)(48 m/s) + (75 kg)(0 m/s) = (0.105 kg)(v) + (75 kg)(v)
5.04 = 75.105v
v = 0.067 m/s, or 6.7 x 10-2 m/s
2. * 35 g = 0.035 kg
Momentumbefore
=
Momentumafter
(0.035 kg)(v) + (5 kg)(0 m/s) = (0.035 kg)(8.6 m/s) + (5 kg)(8.6)
0.035v = 43.301
v = 1237 or 1.237 103 m/s
3. Momentumbefore
=
Momentumafter
(0.035 kg)(475 m/s) + (2.5 kg)(0 m/s) = (0.035 kg)(275 m/s) + (2.5 kg)(v)
16.6 = 9.6 + 2.5v
v = 2.8 m/s
4.
5.
6.
7. momentum before = momentum after
(mv) before = (mv) after
(5m)(10km/hr) = (5m + m)(v)
50m = 6m(v)
v = 8.3 km/hr
8.
a)
x component:
(16.6)(7.13) + (29.1)(0) = (16.6 + 29.1)(v)
118.358 = 45.7v
vx = 2.5898 m/s
y component:
(16.6)(0) + (29.1)(5.28) = (16.6 + 29.1)(v)
153.648 = 45.7v
vy = 3.3621 m/s
vr2 = vx2 + vy2
vr2 = (2.5898)2 + (3.3621)2
vr = 4.243 m/s
b) tanθ = opp/adj
tanθ = 3.3621/2.5898
θ = 52.38o north of east