2019-03-01_Physics_Times

fraction of mechanical energy remains stored as

deformation potential energy in the bodies.

In an inelastic collision, the particle do not regain
their shape and size completely after collision.

Collision is said to be perfectly inelastic if both
the particles stick together after collision and move
with same velocity,

Velocity of separation along line of impact

Velocity of approach along line of impact

e

2 1

1 2

v v

u u







u u 1 & 2 are components of velocities of 1 & 2
along normal direction before collision.
v v 1 & 2 are components of velocities of 1 & 2 along
normal direction after collision.
e = 1 Kinetic Energy is conserved

(^)  Elastic collision.
 e = 0 Kinetic Energy is not conserved
(^)  Perfectly Inelastic collision.
0 < e < 1Kinetic Energy is not conserved
 Partial elastic or inelastic collision.
A ball of mass m hits a floor with a speed v 0
making an angle of incidence  with the normal.
The coefficient of restitution is e.
 After collision components of velocity are
v 0 sin and ev 0 cos
2 2
 v' ( sin ) ( cos )v 0  ev 0  and
tan
tan
e

 
For elastic collision, e = 1 v v' 0 and  
If a mass is added or ejected from a system, at rate
 kg/s and relative velocity vrel (w.r.t. the
system), then the thrust force FTh exerted by this
mass on the system has magnitude vrel.

th rel
dm
F v
dt
 
  
 
 
We can use another form of Newton’s 2 nd law,,

i.e., F F maext Th

  

Where Th r

dm

F v

dt



 

Where vr



is the relative velocity of incoming

mass or ejected mass w.r.t. the main body.

A rocket with initial mass m 0 is ejecting the gases

with relative velocity vr. The rate with which the

rocket ejects gases is.

dm

dt



  Initial velocity is

u.

ln^0

r

m

v u v gt

m

 

   

 

If the rocket is in free space then g= 0

n^0

r

m

v u v l

m

 

   

 

12. Inelastic collision

13. Perfectly inelastic

14. Coefficient of restitution (e)

15. Collision of a ball to a horizontal surface

16. Variable Mass system

17. Rocket Propulsion

A book is lying on the table. What is the angle

between the action of the book on the table and

the reaction of the table on the book?

(a) 0 (b) 30  (c) 45  (d) 180

Three blocks are in equilibrium as shown in figure.

the tension in the string present between the blocks

1 kg & 5 kg is

Newtons Laws of Motion & Friction & Circular

Motion

1.

2.

