In Figure A, the shape of the pillar has changed under the action of the athlete's force, which shows that the force can deform the object.

In the horizontal direction, the box is in equilibrium under the action of horizontal tension F= 10N and sliding friction f, and the equilibrium condition is: f = f = 10n.

Due to the inertia of the wooden box, after the tension is removed, the box continues to move forward due to inertia.

Friction f is related to the contact surface and the pressure between the box and the ground. After the tension is removed, the pressure between the contact surface and the box and the ground remains unchanged, and the friction force on the box remains unchanged, F = 10N.

So, the answer is: sexual change; Inertia; 10.