- #1
bob1182006
- 492
- 1
I have 2 problems I just can't seem to get so I'll post both here instead of making 2 threads.
Both of these are from Halliday & Resnick 5th ed chapter 3 Problems.
Problem #1.
1. Homework Statement
A light beam from a satellite-carried laser strikes an object ejected from an accidentally launched ballistic missile. The beam exerts a force of [itex]2.0 * 10^{-5}[/itex] N on the target.
If the "dwell time" of the beam on the target is 2.4s by how much is the object displaced if it is
a) a 280-kg warhead
b) a 2.1-kg decoy?
(These displacements can be measured by observing the reflected beam)
[tex]\triangle x=v_0 t +\frac{1}{2}at^2[/tex]
F=ma
The missile experiences some uknown horizontal acceleration/velocity so I will just ignore those..
It also experiences a downward acceleration of g.
So does the laser beam?
I need to find the sum of the forces to find the acceleration.
[tex]\frac{mg+2.7*10^{-5}}{m}[/tex] for a I get about 9.8 m/s^2 .
Plugging that into the equation I get a displacement of about 56m but the answer should be some micro-meters..
Problem #9.
1. Homework Statement
A chain consisting of five links, each with mass 100g, is lifted vertically with a constant a =2.5m/s^2.
Find
a) the forces acting between adjacent links
b) the force F exerted on the top link by the agent lifting the chain
c) the net force on each link
F=ma
2.5m/s^2 up
-9.8m/s^2 up
a total of -7.3m/s^2 up
for a.
add up the masses of link+links beneath it and then multiply by 7.3m/s^2 to get a force of:
for the top most link
.5kg*7.3m/s^2 = 3.65 N being exerted on the top link.
Which is completely wrong :/.
for b.
find the total mass and multiply by 7.3m/s^2
F=.5kg*7.3m/s^2=3.65 N
again completely wrong..
for c.
Somehow I got this right...
lowest link force acting upon it is: .1kg*2.5m/s^2 = .25 N
link above it: .2kg*2.5m/s^2=.50 N
...for all others
then subtracting the link force - link below it to get a net force of .25 N on each link.
Any help on either problem is greatly appreciated.
Both of these are from Halliday & Resnick 5th ed chapter 3 Problems.
Problem #1.
1. Homework Statement
A light beam from a satellite-carried laser strikes an object ejected from an accidentally launched ballistic missile. The beam exerts a force of [itex]2.0 * 10^{-5}[/itex] N on the target.
If the "dwell time" of the beam on the target is 2.4s by how much is the object displaced if it is
a) a 280-kg warhead
b) a 2.1-kg decoy?
(These displacements can be measured by observing the reflected beam)
Homework Equations
[tex]\triangle x=v_0 t +\frac{1}{2}at^2[/tex]
F=ma
The Attempt at a Solution
The missile experiences some uknown horizontal acceleration/velocity so I will just ignore those..
It also experiences a downward acceleration of g.
So does the laser beam?
I need to find the sum of the forces to find the acceleration.
[tex]\frac{mg+2.7*10^{-5}}{m}[/tex] for a I get about 9.8 m/s^2 .
Plugging that into the equation I get a displacement of about 56m but the answer should be some micro-meters..
Problem #9.
1. Homework Statement
A chain consisting of five links, each with mass 100g, is lifted vertically with a constant a =2.5m/s^2.
Find
a) the forces acting between adjacent links
b) the force F exerted on the top link by the agent lifting the chain
c) the net force on each link
Homework Equations
F=ma
The Attempt at a Solution
2.5m/s^2 up
-9.8m/s^2 up
a total of -7.3m/s^2 up
for a.
add up the masses of link+links beneath it and then multiply by 7.3m/s^2 to get a force of:
for the top most link
.5kg*7.3m/s^2 = 3.65 N being exerted on the top link.
Which is completely wrong :/.
for b.
find the total mass and multiply by 7.3m/s^2
F=.5kg*7.3m/s^2=3.65 N
again completely wrong..
for c.
Somehow I got this right...
lowest link force acting upon it is: .1kg*2.5m/s^2 = .25 N
link above it: .2kg*2.5m/s^2=.50 N
...for all others
then subtracting the link force - link below it to get a net force of .25 N on each link.
Any help on either problem is greatly appreciated.