PHYSICS 131
(http://www.google.com/)
Search
HOMEWORK 7
A OneDimensional Inelastic Collision
Find the magnitude p_i of the total initial momentum of the twoblock system.
p_i = m1v1+m2v2
(v2=0)
p_i = m1v1
Find v_f, the magnitude of the final velocity of the twoblock system.
p_i = p_f
m1v1+m2v2 = m1v_f1+m2v_f2
(v2=0)
m1v1 = (m1+m2)v_f
v_f = (m1v1)/(m1+m2)
What is the change deltaK = K_fK_i in the system's kinetic energy due to collision?
deltaK = [(1/2)m1(v_f1^2) + (1/2)m2(v_f2^2)]  [(1/2)m1(v1^2) + (1/2)m2(v2^2)]
(v2=0 and v_f1 = v_f2)
deltaK = [(1/2)(m1+m2)(v_f^2)]  [(1/2)m1(v1^2)]
*Note : Answer is negative
Problem 9.9
What is the mass of the second car?
p_i = p_f
m1v1+m2v2 = m1v_f1+m2v_f2
(v2=0
and v_f1=v_f2)
m1v1 = (m1+m2)v_f
m2 = [(m1v1)/v_f]  m1
Homework 7  Physics 131
http://physics131.webs.com/homework7.htm
1 of 8
12/21/10 8:51 PM
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentA Bullet Is Fired into a Wooden Block
Which of the following best describes this collision?
Perfectly Inelastic
(Pefectly Elastic: No loss of Kinetic Energy, Partially Inelastic: Loss of Kinetic Energy but objects don't stick, Perfectly
Inelastic: Loss of Kinetic Energy and objects stick)
Which of the following quantities, if any, are conserved during this collission?
Momentum Only
(Remember: Momentum is always conserved regardless of being an elastic or inelastic collision is there is no external
force)
What is the speed of the block/bullet system after the collission?
mbvb+mw vw = mbv_fb+mw v_fw
(vw=0, v_fb=v_fw and vb=vi)
mbvi = (mb+mw)v_f
v_f = (mbvi)/(mb+mw)
Problem 9.13
Calculate the velocity of the boat immediately after.
m1v1+m2v2 = m1v_f1+m2v_f2
(v1=v2=0 ,since everything is initially at rest)
0 = m1v_f1+m2v_f2
v_f2 = ((m1v1)/m2)
,where m1=mass of package and m2=mass of child and boat combined
*Note: The answer is negative since the child and boat move in the negative xaxis
Problem 9.35
Assuming a perfectly elastic collision, what will be the speed of each object after the collision?
Since kinetic energy is conserved in elastic collision.
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '03
 Rijssenbeek
 Kinetic Energy, Mass, Momentum, Work, Wnc, mbvb

Click to edit the document details