Question

Forensic scientists can determine the speed at which a rifle fires a bullet by shooting into a heavy block hanging by a wire. As the bullet embeds itself in the block, the block and embedded bullet swing up; the impact speed is determined from the maximum angle of the swing (a) Which would make the block swing higher, a 0.204 Ruger bullet of mass 2.14 g and muzzle speed 1290 m/s or a 7-mm Remington Magnum bullet of mass 9.71 g and muzzle speed 948 m/s? Assume the bulets enter the block right after leaving the muzzle of the rifle. The Ruger bullet will make the block swing higher The Remington bullet will make the block swing higher b) Using your answer in part (a), determine the mass of the block so that when hit by the bullet it will swing through a 60 angle. The block hangs from wire of length 1.17 m and negligible mass. 2.72 (c) What is the speed of a 9-g bullet that causes the block to swing upward through a 35° angle? 744 m/s Two different bullets are shot with different speeds into a heavy block of unknown mass. We can use conservation of momentum and conservation of energy in order to determine which case will cause the block to swing higher. Once we know which bullet to use, we can apply the same procedure to calculate the mass of the wooden block. We will then use the same wooden block to calculate the speed a third bullet is traveling to cause the block to swing a certain height. eBook