Please help! Tricky Science question!?

Question

An object accelerates (changes it's speed) only if the forces acting on it in one direction are greater than the forces in the opposite direction, All the following objects will accelerate EXCEPT:

A) A ball striking a wall, in which the force of the ball on the wall is equal to the force of the wall on the ball.

B) A gas balloon in which the buoyant force is greater than it's weight and air resistance.

C) A man in a parachute when the air resistance is less than his weight.

D) a rocket fired straight up, when the engine thrust is equal to the air resistance

E) An airplane in horizontal flight when the thrust of the engine is equal to the drag of the air

Answer 1

what do you find tricky?

In statement E the forces are stated to be in balance.

So the plane flies at constant speed.

There you go.

Answer 2

it's (e), i agree with arch.'s answer.

don't be confused any more.