Answer:
None of the above.
The correct answer would be momentum
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Car X traveled 3d distance in t time. Car Y traveled 2d distance in t time. Therefore, the speed of car X, is 3d/t, the speed of car Y, is 2d/t. Since speed is the distance taken in a given time.
In figure-2, they are at the same place, we are asked to find car Y's position when car X is at line-A. We can calculate the time car X needs to travel to there. Let's say that car X reaches line-A in t' time.

Okay, it takes t time for car X to reach line-A. Let's see how far does car Y goes.

We found that car Y travels 2d distance. So, when car X reaches line-A, car Y is just a d distance behind car X.
<u>Answer:</u>
For 1: The correct option is Option C.
For 3: The final velocity of the opponent is 1m/s
<u>Explanation: </u>
During collision, the energy and momentum remains conserved. The equation for the conservation of momentum follows:
...(1)
where,
are the mass, initial velocity and final velocity of first object
are the mass, initial velocity and final velocity of second object
<u>For 1:</u>
We are Given:

Putting values in equation 1, we get:

Hence, the correct answer is Option C.
Impulse is defined as the product of force applied on an object and time taken by the object.
Mathematically,

where,
F = force applied on the object
t = time taken
J = impulse on that object
Impulse depends only on the force and time taken by the object and not dependent on the surface which is stopping the object.
Hence, the impulse remains the same.
Let the speed in right direction be positive and left direction be negative.
We are Given:

Putting values in equation 1, we get:

Hence, the final velocity of the opponent is 1m/s and has moved backwards to its direction of the initial velocity.