(a) Figure P9.36 shows three points in the operation of the ballistic pendulum discussed in Example 9.6 (and shown in Fig. 9.10b). The projectile approaches the pendulum in Figure P9.36a. Figure P9.36b shows the situation just after the projectile is captured in the pendulum. In Figure P9.36c, the pendulum arm has swung upward and come to rest momentarily at a height A above its initial position. Prove that the ratio of the kinetic energy of the projectile–pendulum system immediately after the collision to the kinetic energy immediately before is m1|/(m1 + m2). (b) What is the ratio of the momentum of the system immediately after the collision to the momentum immediately before? (c) A student believes that such a large decrease in mechanical energy must be accompanied by at least a small decrease in momentum. How would you convince this student of the truth?
Figure P9.36 Problem. 36 and 43. (a) A metal ball moves toward the pendulum. (b) The ball is captured by the pendulum. (c) The ball–pendulum combination swings up through a height h before coming to rest.
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Chapter 9 Solutions
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- (a) Figure P9.36 shows three points in the operation of the ballistic pendulum discussed in Example 9.6 (and shown in Fig. 9.10b). The projectile approaches the pendulum in Figure P9.36a. Figure P9.36b shows the situation just after the projectile is captured in the pendulum. In Figure P9.36c, the pendulum arm has swung upward and come to rest momentarily at a height A above its initial position. Prove that the ratio of the kinetic energy of the projectilependulum system immediately after the collision to the kinetic energy immediately before is m1|/(m1 + m2). (b) What is the ratio of the momentum of the system immediately after the collision to the momentum immediately before? (c) A student believes that such a large decrease in mechanical energy must be accompanied by at least a small decrease in momentum. How would you convince this student of the truth? Figure P9.36 Problem. 36 and 43. (a) A metal ball moves toward the pendulum. (b) The ball is captured by the pendulum. (c) The ballpendulum combination swings up through a height h before coming to rest.arrow_forwardSven hits a baseball (m = 0.15 kg). He applies an average force of 50.0 N. The ball had an initial velocity of 35.0 m/s to the right and a final velocity of 40.0 m/s to the left as viewed by a fan in the stands. a. What is the impulse delivered by Svens bat to the baseball? b. How long is his bat in contact with the ball?arrow_forwardA submarine with a mass of 6.26 106 kg contains a torpedo with a mass of 354 kg. The submarine fires the torpedo at an angle of 25 with respect to the horizontal as shown in Figure P10.42. a. If the submarine and the torpedo were initially at rest and the torpedo left the submarine with a speed of 89.2 m/s, what is the recoil speed of the submarine? b. What is the direction of recoil of the submarine? FIGURE P10.42arrow_forward
- A rocket has total mass Mi = 360 kg, including Mfuel = 330 kg of fuel and oxidizer. In interstellar space, it starts from rest at the position x = 0, turns on its engine at time t = 0, and puts out exhaust with relative speed ve = 1 500 m/s at the constant rate k = 2.50 kg/s. The fuel will last for a burn time of Tb = Mfuel/k = 330 kg/(2.5 kg/s) = 132 s. (a) Show that during the burn the velocity of the rocket as a function of time is given by v(t)=veln(1ktMi) (b) Make a graph of the velocity of the rocket as a function of time for times running from 0 to 132 s. (c) Show that the acceleration of the rocket is a(t)=kveMikt (d) Graph the acceleration as a function of time. (c) Show that the position of the rocket is x(t)=ve(Mikt)ln(1ktMi)+vet (f) Graph the position during the burn as a function of time.arrow_forwardA ball of mass 50.0 g is dropped from a height of 10.0 m. It rebounds after losing 75% of its kinetic energy during the collision process. If the collision with the ground took 0.010 s, find the magnitude of the impulse experienced by the ball.arrow_forwardA model rocket is shot straight up and explodes at the top of its trajectory into three pieces as viewed from above and shown in Figure P10.44. The masses of the three pieces are mA = 100.0 g, mB = 20.0 g, and mC = 30.0 g. Immediately after the explosion, piece A is traveling at 1.50 m/s, and piece B is traveling at 7.00 m/s in a direction 30 below the negative x axis as shown. What is the velocity of piece C? FIGURE P10.44 Problems 44 and 45. 45. We can use the conservation of momentum (Eq. 10.9). The total initial momentum is zero, so the sum of all the final momenta should be zero. mAvAf+mBvBf+mCvCf=0 This velocities for A and B can be expressed as vectors. vAf=1.50jm/svBf=(7.00im/s)cos30(7.00jm/s)sin30=(6.06i3.50j)m/s We can now solve the momentum equation. (100.0g)(1.50jm/s)+(20.0g)(6.06i3.50j)m/s+(30.0g)vCf=0vCf=(4.04i2.67j)m/s The velocity of piece C is down and to the right as expected.arrow_forward
- One object (m1 = 0.200 kg) is moving to the right with a speed of 2.00 m/s when it is struck from behind by another object (m2 = 0.300 kg) that is moving to the right at 6.00 m/s. If friction is negligible and the collision between these objects is elastic, find the final velocity of each.arrow_forwardA cannon is rigidly attached to a carriage, which can move along horizontal rails but is connected to a post by a large spring, initially unstretchcd and with force constant k = 2.00 104 N/m, as shown in Figure P8.60. 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?arrow_forwardA proton with an initial speed of 2.00 108 m/s in the x direction collides elastically with another proton initially at rest. The first protons velocity after the collision is 1.64 108 m/s at an angle of 35.0 with the horizontal. What is the velocity of the second proton after the collision?arrow_forward
- A 2500 kg cannon, initially at rest, fires an 80 kg shell horizontally, with a speed of 600 m/s. What is the maximum possible recoil velocity of the cannon?arrow_forward11. a. A 99.5 kg lumberjack is standing on log A. Initially he's at rest. Then he starts running forward and jumps off the log. If he jumps forward with a velocity of 3.075 m/s, what is the recoil velocity of the log? The log has a mass of 115 kg. Assume all velocity are relative to the ground. Previous submissions: b. Our lumberjack than lands on log B, also initially at rest. Both logs have the same mass. What's the final velocity of log B with our lumberjack landed and riding it. Previous submissions:arrow_forwardA 10 g bullet is fired into a 1.0 kg wood block, where it lodges. Subsequently, the block slides 4.2 m across a wood floor (uk = 0.2). What was the bullet's speed. Use g = 10 N/kg.arrow_forward
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