What is the final angular velocity omega_f of the CD? c. How many complete revol

Question

What is the final angular velocity omega_f of the CD? c. How many complete revolutions has the CD made during the time it was accelerating? You take your DeLorean to Hill Valley circa 1885 to save Doc Brown from Mad Showing off skills you learned duck-hunting, you fire a 15 g bullet at a 1 kg block of wood. The bullet leaves the barrel at 400 m/s and embeds itself Is the resulting collision elastic or inelastic? State how you know and what that means for any related conservation laws. Calculate the total momentum and the total energy before the collision. The block rests on a frictionless floor. With what speed does the block slide away after being hit by the bullet? Calculate the total momentum and the total energy after the collision. The block then slides up a ramp at angle theta = 35 degree. How high above the floor is the block when it comes to a stop? How far along the surface of the ramp did it travel?

Explanation / Answer

Given,

m1 = 15 g = 0.015 kg ; m2 = 1 kg ; u1 = 400 m/s ; u2 = 0

1)The resulting collision is inelastic, since he bullet embeds into the block and the system of bullet and block travels together with the same speed. So the energy is not consvered, and hence the collision is inelastic.

2)The total momentum and the energy of the system before collsion is due to the bullet only since the block is stationary.

Pi = m1u1

P1 = 0.015 x 400 = 6 kg-m/s

Ei = 1/2 m1 u1^2 = 0.5 x 0.015 x 400^2 = 1200 J

Hence, Pi = 6 kg-m/s and Ei = 1200 J

3)from the conservation of the linear momentum,

Pi = Pf

m1 u1 = (m1 + m2)Vf

Vf = m1 u1/(m1 + m2)

Vf = 0.015 x 400/(0.015 + 1) = 5.911 m/s

Hence, speed of block after being hit by the bullet is: Vf = 5.911 m/s

4)The total momentum of the block bullet system will be:

Pf = (m1 + m2) Vf

Pf = (0.015 + 1) 5.911 = 6 kg- m/s

Ef = 1/2 (m1 + m2) Vf^2

Ef = 0.5 x (0.015 + 1) 5.911^2 = 17.73 J

Hence, Pf = 6 kg-m/s and Ef = 17.73 J

5)from conservation of energy

1/2 (m1 + m2) Vf^2 = (m1 + m2) g h

h = Vf^2/2g = 5.911^2/2 x 9.81 = 1.781 m

from trigonometry,

h/x = sin(theta)

x = h/sin(theta) = 1.781/sin35 = 3.11 m

Hence, h = 1.781 m and x = 3.11 m

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.