You have learned about Newton's Second Law of motion earlier in this chapter.
Newton's Second Law describes the relationship between the motion of an object and the net force on the object. We said that the motion of an object, and therefore its momentum, can only change when a resultant force is acting on it. We can therefore say that because a net force causes an object to move, it also causes its momentum to change. We can now define Newton's Second Law of motion in terms of momentum.
Newton's Second Law of Motion (N2)
The net or resultant force acting on an object is equal to the rate of change of momentum.
Mathematically, Newton's Second Law can be stated as:
$${F}_{net}=\frac{\Delta p}{\Delta t}$$
Impulse
Impulse is the product of the net force and the time interval for which the force acts. Impulse is defined as:
Impulse is equal to the change in momentum of an object. From this equation we see, that for a given change in momentum,
${F}_{net}\Delta t$ is fixed. Thus, if
${F}_{net}$ is reduced,
$\Delta t$ must be increased (i.e. a smaller resultant force must be applied for longer to bring about the same change in momentum). Alternatively if
$\Delta t$ is reduced (i.e. the resultant force is applied for a shorter period) then the resultant force must be increased to bring about the same change in momentum.
A 150 N resultant force acts on a 300 kg trailer. Calculate how long it takes this force to change the trailer's velocity from 2 m
$\xb7$ s
${}^{-1}$ to 6 m
$\xb7$ s
${}^{-1}$ in the same direction. Assume that the forces acts to the right.
The question explicitly gives
the trailer's mass as 300 kg,
the trailer's initial velocity as 2 m
$\xb7$ s
${}^{-1}$ to the right,
the trailer's final velocity as 6 m
$\xb7$ s
${}^{-1}$ to the right, and
the resultant force acting on the object
all in the correct units!
We are asked to calculate the time taken
$\Delta t$ to accelerate the trailer from the 2 to 6 m
$\xb7$ s
${}^{-1}$ . From the Law of Momentum,
It takes 8 s for the force to change the object's velocity from 2 m
$\xb7$ s
${}^{-1}$ to the right to 6 m
$\xb7$ s
${}^{-1}$ to the right.
A cricket ball weighing 156 g is moving at 54 km
$\xb7$ hr
${}^{-1}$ towards a batsman. It is hit by the batsman back towards the bowler at 36 km
$\xb7$ hr
${}^{-1}$ . Calculate
the ball's impulse, and
the average force exerted by the bat if the ball is in contact with the bat for 0,13 s.
The question explicitly gives
the ball's mass,
the ball's initial velocity,
the ball's final velocity, and
the time of contact between bat and ball
We are asked to calculate the impulse
$$\mathrm{Impulse}=\Delta p={F}_{net}\Delta t$$
Since we do not have the force exerted by the bat on the ball (F
${}_{net}$ ), we have to calculate the impulse from the change in momentum of the ball. Now, since
Similarly, 36 km
$\xb7$ hr
${}^{-1}$ = 10 m
$\xb7$ s
${}^{-1}$ .
Let us choose the direction from the batsman to the bowler as the positive direction. Then the initial velocity of the ball is
${v}_{i}$ = -15 m
$\xb7$ s
${}^{-1}$ , while the final velocity of the ball is
${v}_{f}$ = 10 m
$\xb7$ s
${}^{-1}$ .
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
In this morden time nanotechnology used in many field .
1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc
2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc
3- Atomobile -MEMS, Coating on car etc.
and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change .
maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.