PreQuiz 7.2 - Conservation of Momentum .:. Go Up

The Formula:

p = momentum in kgm/s
v = velocity in m/s  Draw a picture - make to the right +, left -
m = mass in kg

The Prequiz:

1. A bullet going 481 m/s imbeds in a stationary block of wood.  The bullet and block combo are going 5.27 m/s after the collision, and the combo has a mass of 12.1 kg (Bullet and block).  What was the mass of the bullet? (0.133 kg)

mv = (m+m)v

m(481 m/s) = (12.1 kg)(5.27 m/s)

2. A 65 kg person dives 3.68 m/s to the right off of a 23 kg cart.  What is the velocity of the cart if the cart and person were initially at rest? (10. m/s to the left)

0 = mv + mv

0 = (65 kg)(3.68 m/s) + (23 kg)v

v = -10. m/s (left)

3. 68 kg-Francois running 7.8 m/s jumps on a 45.3 kg cart already rolling at 2.3 m/s in the same direction.  What speed are they going after he jumps on? (5.6 m/s)

mv + mv = (m + m)v

(68 kg)(7.8 m/s) + (45.3 kg )(2.3 m/s) = (68 kg + 45.3 kg)v

v = 5.6 m/s (in the same direction)

4.  A 1240 kg Toyota Camry going 12.0 m/s to the east, strikes a 2530 kg SUV going west at 16.3 m/s.  What is the velocity of the wreckage after the collision?  (6.99 m/s to the west)

mv + mv = (m + m)v

Make to the east positive:

(1240 kg)(12.0 m/s) + (2530 kg)(-16.3 m/s) = (1240 kg + 2530 kg)v

5. A 65 kg person is riding a 23 kg cart to the right at 3.15 m/s.  What speed must he dive off the cart, and in what direction, to give the cart a velocity of 22.3 m/s to the right? (3.6 m/s to the left)

(m + m)v = mv + mv

Make to the right positive

(65 kg + 23 kg)(3.15 m/s) = (65 kg)v + (23 kg)(22.3 m/s)