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A bullet of mass m = 8.00 g is fired into a block of mass M = 170 g that is init

ID: 2143479 • Letter: A

Question

A bullet of mass m = 8.00 g is fired into a block of mass M = 170 g that is initially at rest at the edge of a table of height h = 1.00 m (see figure below). The bullet remains in the block, and after the impact the block lands d = 1.60 m from the bottom of the table. Determine the initial speed of the bullet.
m/s

A bullet of mass m = 8.00 g is fired into a block of mass M = 170 g that is initially at rest at the edge of a table of height h = 1.00 m (see figure below). The bullet remains in the block, and after the impact the block lands d = 1.60 m from the bottom of the table. Determine the initial speed of the bullet.

Explanation / Answer


let the speed is x m/s and speed of block after collision be v m/s

momentum would be conserved

therefore

initial momentum = final momentum

m1*v1 = (m1+m2)v2

where m1 & m2 are masses of bullet and block ; v2(v) is final velocity of block - bullet system

8 * x = (170 + 8) * v

v = 8x/ 178m/s

time taken to fall = sqrt(2 h/g)

= sqrt(2 * 1/9.8)

= sqrt(10) / 7

=0.451 sec

distance covered in x dir = product of velocity and time taken

1.6 = 8x/178 * 0.451

x= 78.93 m/s