Question

Below are birds-eye views of six identical toy cars moving to the right at 2 m/s. Various forces act on the cars with magnitudes and directions indicated below. All forces act in the horizontal plane and are either parallel or at 45 or 90 degrees to the car's motion. Rank these cars on the basis of their speed a short time (ie. before any car's speed can reach zero) after the forces are applied. Rank from largest to smallest. To rank items as equivalent, overlap them.

Answer 1

All cars have the same speed before the forces are applied ( v = 2 m/s ).
After that rank is:
1. Largest: 6th car ;  Fr = 10 N,
2. 1st car ;  Fr = 2.95 N.
3. After that: 2nd, 3rd and 5th car ;  Fr = 0 N
4. Smallest : 4th car ;  Fr = - 2.04 N.