Question

Two cars are parked on a street. A third car hits the back of the second car and causes all of the cars to move. (Ignore the distance between the cars). Calculate:
(a)The acceleration of the whole system;
(b)the net force on each car;
(c)the contact force that each car exerts on the neighbor;
(d)if all the masses are equal and 1200kg., and F=960 Newtons, give numerical answers to the previous parts.

Answer 1

You can not find the forces or acceleration without more information. The only thing you can use is the First Law, conservation of momentum, which will give you final speed if they stick together. (1/3 the original speed)
To answer questions about force and acceleration, you must know the time duration of the crash. ( change in momentum = integral of F dt)
Where did you get this question? Didd you make it up yourself or is there more information that you have not typed. Your other question about the mountain climber is also unanswerable as stated.