Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

A 1.5 meter long uniform rod is pivoted about a pin through one end, so it is fr

ID: 1907929 • Letter: A

Question

A 1.5 meter long uniform rod is pivoted about a pin through one end, so it is free to rotate in a vertical plane. Consider the rod to have no mass. A 3.75kg mass is attached to the far end of the rod. At that point a 10. 45g bullet is fired at the rod with speed 213m/s. It hits the mass, moving perpendicular to the mass and rod and is embedded in it. - If the mass was initially at rest and there is no friction at the piviot, what is the speed of the mass after the bullet hits it? -How much kinetic energy is lost in collision?

Explanation / Answer

a)

m1 v1 = (m1+m2) v

v = m1 v1 / (m1+m2) = 0.045*213/(0.045+3.75)

v = 2.53 m/s

b)

0.5 m1 v1^2 - 0.5 (m1+m2) v^2

= 0.5 * 0.045*213*213 - 0.5*3.75*2.52569*2.52569

= 1009 J