# physics

posted by .

A projectile of mass m moves to the right with a speed vi. The projectile strikes and sticks to the end of a stationary rod of mass M, of length d, that is pivoted about a frictionless axle through its center.

(a) Find the angular speed of the system right after the collision. (Use v_i for vi, m, M, and d as appropriate in your equation.)
(b) Determine the fractional loss in mechanical energy due to the collision. (Use v_i for vi, m, M, and d as appropriate in your equation.)
fractional loss of energy

I got part a correct and it's (12mv_i^2)/((m+M)d^2)
For part b is it just the final kinetic energy over the initial kinetic energy? If so, why do I keep getting the same answer as part a?

• physics -

for part b, your final KE is rotational KE which is now 1/2 I w^2 where I consists of the rod mass distributed, and the mass of the initial stuff at some rotational distance. You cant get the same answer as a), as the units are different. THe units in a) are sec^-1, and in b) should be unitless.

• physics -

so would it be (Iw^2)/(mv^2)?

• physics -

Yes, depending on what you put in for final I, w, and the intial v.

• physics -

actually, since b) asked for fractional loss, it would be that fraction subtracted from 1.

• physics -

What did you put in for I

## Similar Questions

A thin uniform rod (length = 1.3 m, mass = 4.1 kg) is pivoted about a horizontal frictionless pin through one of its ends. The moment of inertia of the rod through this axis is 1/3 m L2. The rod is released when it is 55° below the …
2. ### Physics

A ballistic pendulum consists of an arm of mass M and length L = 0.52 m. One end of the arm is pivoted so that the arm rotates freely in a vertical plane. Initially, the arm is motionless and hangs vertically from the pivot point. …
3. ### Physics

A uniform rod AB of length 2a and mass M is freely pivoted at A and is held with B vertically above A. It is then allowed to fall and when B is vertically below A it strikes a stationary particle , also of mass M,which sticks to the …
4. ### Physics

A thin uniform rod (length = 1.3 m, mass = 3.2 kg) is pivoted about a horizontal frictionless pin through one of its ends. The moment of inertia of the rod through this axis is (1/3)mL2. The rod is released when it is 50° below the …
5. ### Physics

A ballistic pendulum consists of an arm of mass M and length L = 0.485 m. One end of the arm is pivoted so that the arm rotates freely in a vertical plane. Initially, the arm is motionless and hangs vertically from the pivot point. …
6. ### Physics

A projectile is launched at an angle of 34.0o above the horizontal. The projectile has a mass of 1.50 kg and is given an initial speed of 20.0 m/s. a) What is the initial kinetic energy of the projectile?
7. ### Physics

A mass of 100g is attached to one end of a massless rod, 10cm in length, which is pivoted about the opposite end. The rod is held vertical, with the mass at the top, and released. The rod swings. A. What is the speed of the mass at …
8. ### physics

A piece of putty of mass m = 0.75 kg and velocity v = 2.5 m/s moves on a horizontal frictionless surface. It collides with and sticks to a rod of mass M = 2 kg and length L = 0.9 m which pivots about a fixed vertical axis at the opposite …
9. ### general physics

An axle of a mass of 10 kg, length 10 cm and radius .1 m is free to rotate about the axis which runs the length of the axle, throuhh it's center. A chain of mass 4kg is fastened to the axle at one end, wound exactly 6 times around …
10. ### mit

A small circular block of mass M traveling with a speed v on a frictionless table collides and sticks to the end of a thin rod of with length D and mass M. The picture shows a top down view of the block and rod on the frictionless …

More Similar Questions