Chapter 8 – part A 2D collisions Center of Mass System of Particles

Exercise 8.26

26.

Two automobiles of equal mass approach an intersection. One vehicle is traveling with velocity 13.0 m/s toward the east, and the other is traveling north with speed

v

2

i

. Neither driver sees the other. The vehicles collide in the intersection and stick together, leaving parallel skid marks at an angle of 55.0

° north of east. The speed limit for both roads is 35 mi/h, and the driver of the northward-moving vehicle claims that he was within the speed limit when the collision occurred. Is he telling the truth?

Exercise 8.30

30.

A 0.300-kg puck, initially at rest on a horizontal, frictionless surface, is struck by a 0.200-kg puck moving initially along the

x

axis with a speed of 2.00 m/s. After the collision, the 0.200-kg puck has a speed of 1.00 m/s at an angle of

θ

= 53.0

° to the positive

x

axis. (a) Determine the velocity of the 0.300-kg puck after the collision. (b) Find the fraction of kinetic energy lost in the collision.

Exercise 8.34

34.

A water molecule consists of an oxygen atom with two hydrogen atoms bound to it. The angle between the two bonds is 106 °. If the bonds are 0.100 nm long, where is the center of mass of the molecule?

Exercise 8.39

39.

Romeo (77.0 kg) entertains Juliet (55.0 kg) by playing his guitar from the rear of their boat at rest in still water, 2.70 m away from Juliet who is in the front of the boat. After the serenade, Juliet carefully moves to the rear of the boat (away from shore) to plant a kiss on Romeo’s cheek. How far does the 80.0-kg boat move toward the shore it is facing?

Exercise 8.56

56.

Two particles with masses

m

and 3

m

are moving toward each other along the

x

axis with the same initial speeds

v i

. Particle

m

is traveling to the left, and particle 3

m

is traveling to the right. They undergo an elastic glancing collision such that particle

m

is moving downward after the collision at right angles from its initial direction. (a) Find the final speeds of the two particles. (b) What is the angle

θ

at which the particle 3

m

is scattered?

Exercise 8.58

58.

A cannon is rigidly attached to a carriage, which can move along horizontal rails but is connected to a post by a large spring, initially unstretched and with force constant

k

= 2.00 × 10 4 N/m, as shown in Figure P8.58. The cannon fires a 200-kg projectile at a velocity of 125 m/s directed 45.0

° above the horizontal. (a) Assuming that the mass of the cannon and its carriage is 5 000 kg, find the recoil speed of the cannon. (b) Determine the maximum extension of the spring. (c) Find the maximum force the spring exerts on the carriage. (d) Consider the system consisting of the cannon, carriage, and projectile. Is the momentum of this system conserved during the firing? Why or why not?