An object accelerates (changes its speed) only if the forces acting on it in one direction are greater than the forces in the opposite direction, All of 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 its weight and air resistance
C) a man in a parachute when the air resistance is less than his weight
D) an airplane in horizontal flight when the thrust of the engine is equal to the drag of the air
Which situation has unbalanced forces? The choices reveal the answer.
To determine which object will not accelerate, we need to consider Newton's Second Law of Motion, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (a = F/m).
Let's analyze each scenario:
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
In this case, the forces on the ball are balanced, meaning that there is no net force acting on it. Therefore, the ball will not accelerate. So, this scenario does not show acceleration.
B) a gas balloon in which the buoyant force is greater than its weight and air resistance
In this scenario, the buoyant force (the upward force exerted by a fluid, in this case, air) is greater than the weight and air resistance (a force opposing the motion of the balloon). As a result, there is a net force acting upward, causing the balloon to accelerate upward. So, this scenario shows acceleration.
C) a man in a parachute when the air resistance is less than his weight
In this case, the air resistance acts upward, opposing the downward force of gravity. If the air resistance is less than the man's weight, the net force will be downward, resulting in acceleration downward. So, this scenario shows acceleration.
D) an airplane in horizontal flight when the thrust of the engine is equal to the drag of the air
In this scenario, if the thrust of the airplane's engine is equal to the drag force of the air (a force that opposes the motion of the airplane), then the net force is zero. Without a net force, the airplane will not accelerate. So, this scenario does not show acceleration.
Based on the analysis, the correct answer is D) an airplane in horizontal flight when the thrust of the engine is equal to the drag of the air.