A(n) 7 g bullet is fired into a 122 g block that is initially at rest at the edge of a frictionless table of height 0.9 m. The bullet remains in the block, and after impact the block lands 1.7 m from the bottom of the table.The acceleration of gravity is 9.8 m/s2. Find the initial speed of the bullet. Answer in m/s

Answer 1

Use g and the height of the table (H) to get the time that it takes the block and bullet to fall.

t = sqrt(2H/g)= 0.429 s

Then divide 1.7 m by that time to get the (horizontal) velocity of the block/bullet right after impact. Call it v. That horizontal velocity component remains constant as it falls.

Once you have the velocity after impact, use conservation of momentum to get the bullet velocity, V.

m V = (m + M)*v
V = (m + M)*v/m