Question

Given
...
e-Techno Classwork
IX - Physics (Vol 1)
In the absence of dissipative forces in collisions
1) KE - KE
2) KE >KE,
3) KE KE
4) Non
JEE MAIN & ADVANCED
LEVEL
1.
A body of mass 4kg moves with a velocity of 10m/s collide elastically with
another body of mass 8kg at rest. Then the velocity of 8kg body after collisi
1) 4 m/s
2) 6.67 m/s
3) 10 m/s
4) 12 m/s
A marble going at a speed of 2m/s hits another marble of equal mass at re
the collision is perfectly elastic. The velocity of the first after collision
1) 4
2) O
4) 3
3) 2​

Answer 1

Answer:

you are in Narayana e tecno CBSE school??

Explanation:

#dynamite

Answer 2

Answer:

The total amount of mechanical energy, in a closed system in the absence of dissipative forces (e.g. friction, air resistance), remains constant. This means that potential energy can become kinetic energy, or vice versa, but energy cannot “disappear”.

In the absence of dissipation energy of system consists of only mechanical energy i.e kinetic energy 

andpotentialenergy. Since Total energy is conserved and Total energy is equal to mechanical energy,

so,option D is correct

Given,

m=4kg

u=10m/s

t=1.5sec

Lets consider the velocity of body after collision is v.

Impulsive force and momentum relation is,

I=F×t=ΔP. . . . .(1)

From the given graph area under the graph is equal to impulse,

The area under the graph = area of trapezium.

A=I=21(a+b)h

I=21(1.5+0.5)×40=40Ns

equation (1),

I=m(u−v)=40

4(10−v)=40

40−4v=40

4v=0

v=0m/s

The correct option is A.

A marble going at a speed of 2ms-1 hits another marble of equal mass at rest. If the collision is perfectly elastic, then the velocity of the first marble after collision is. Solution : →v1=(m1-m2m1+m2)→u1+(2m2m1+m2)→u2.

Explanation:

hope it helps