Answer:
7.2
J
or
80
%
of the original kinetic energy is lost.
Explanation:
Take A Ball For an Example.
Conservation of momentum says that momentum before a reaction and momentum after a reaction must be equal.
Momentum is the product of mass and velocity, so
(
m
v
)
1
=
(
m
v
)
2
Only moving objects have momentum, so all the momentum beforehand is in the moving ball, so
(
m
v
)
1
=
2
k
g
×
3
m
s
−
1
=
6
N
s
This ball stops moving, and now only the
10
k
g
ball moves, so momentum after the reaction is
(
m
v
)
2
=
10
k
g
×
v
m
s
−
1
We know that this is equal to the momentum before, so
10
×
v
=
6
→
v
=
0.6
m
s
−
1
Now for the second part. Calculating kinetic energy is done by the equation
E
=
1
2
m
v
2
which, before the reaction, is
E
=
1
2
×
2
×
3
2
=
9
J
after the reaction, it will be
E
=
1
2
×
10
×
0.6
2
=
1.8
J
Overall, then, the kinetic energy lost is
Δ
E
=
9
−
1.8
=
7.2
J
or, as a percentage,
9
−
1.8
9
×
100
%
=
80
%
of the kinetic energy is lost.
I Hope This Helps.
