In: Physics
In Fig. 8.3, a bullet of mass 0.01 kg moving horizontally strikes a block of wood of mass 1.5 kg which is suspended as a pendulum. The bullet lodges in the wood, and together they swing upward a distance of 0.40 m. What was the velocity of the bullet just before it struck the wooden block? The length of the string is 2 meters.
Gravitational acceleration = g = 9.81 m/s2
Mass of the bullet = m = 0.01 kg
Mass of the block = M = 1.5 kg
Initial speed of the bullet = V1
Speed of the block and bullet immediately after the collision = V2
By conservation of linear momentum,
Height to which the block and bullet rise after the collision = h = 0.4 m
Length of the string attached to the block = L = 2 m
By conservation of energy the kinetic energy of the block and bullet immediately after the collision is converted into the potential energy of the block and bullet as they go up.
V1 = 423 m/s
Velocity of the bullet just before it struck the wooden block = 423 m/s