Answer: 50 m.
Step-by-step explanation:
Assuming there is only 20N force acting on the object, use F = m * a where F is force, m is mass and a is acceleration.
You'll get a = 2.
Next, write what you know.
acceleration (a) = 2
initial velocity (u) = 5
final velocity (v) = 15
distance (s) = ?
Now, use v² = u² + 2as and find s.