Question

Physics question :- in an elastic collision
-The final linear momentum is equal to initial linear momentum.
Is this correct? Why?

Answer 1

it follows from Newton's Laws.

3rd law, action and reaction are equal and opposite; and 2nd law \(F = \dot p\).

so for a collision where \(F ~dt = d(mv)\), we have \( F_1 = -F_2, \quad d(mv)_1 + d(mv)_2 = 0\)

and it's also true in an inelastic collision

Answer 2

So this is correct

Answer 3

But that is not the answer ,it is incorrect

Answer 4

Oh I think the initial linear momentum is negative of final linear momentum and vice versa ......that's why it is incorrect.

Answer 5

linear momentum of a closed and isolated "system" cannot change when there is no external force

Answer 6

linear momentum of individual objects can change, but the total linear momentum remains constant

Answer 7

Then answer should be correct but it's not.

Answer 8

your question is ambiguous

Answer 9

```
-The final linear momentum is equal to initial linear momentum.
Is this correct? Why?
```


final linear momentum of what ?

Answer 10

Obviously, it should be for complete system

Answer 11

assuming no external force, the linear momentum of system must be same at any point in time

Answer 12

The law of conservation of momentum is not applicable for, say, this system.

Answer 13

Try to answer why.

Answer 14

If we Take example of an elastic collision between a ball and wall
Initial momentum is =MV {M is mass of ball and V velocity)
And final =-MV
(as wall is fixed so velocity of ball is reversed.)

Answer 15

the system must be closed and isolated

Answer 16

Because gravity acts as external force

Answer 17

Plus there are impulsive adhesive forces in the wall.

Answer 18

No, not gravity