Problem 16
Question
A thief stole a box full of valuable articles of weight \(w\) and while carrying it on his head jumped down from a wall of height \(h\) from the ground. Before he reaches the ground, he experienced a load (a) zero (b) \(w / 2\) (c) \(w\) (d) \(2 w\)
Step-by-Step Solution
Verified Answer
The thief experiences a load of zero.
1Step 1: Understanding the Problem
The problem is about a thief jumping down with a box, experiencing a force while falling. This force is linked to the concept of apparent weight when in free fall.
2Step 2: Theoretical Knowledge
When a body is in free fall, it is under the influence of gravity alone, which means that the apparent weight of the body becomes zero, as there is no normal force acting on it.
3Step 3: Applying the Concept
Since the thief and the box are in free fall before reaching the ground, the force of gravity is the only acting force. Thus, the thief experiences an apparent load, or force, of zero.
4Step 4: Choosing the Correct Option
Based on our understanding that the apparent weight is zero during free fall, the correct answer to the problem is option (a) zero.
Key Concepts
Understanding Free FallThe Force of GravityExplaining Normal Force
Understanding Free Fall
Free fall is a fascinating phenomenon where an object is influenced solely by gravity without any other forces acting on it, such as air resistance or friction. This means that during free fall, the object accelerates at the same rate due to gravity, which on Earth is approximately 9.8 m/s².
A remarkable aspect of free fall is that all objects, regardless of their masses, fall with the same acceleration when no other forces are present. This was famously demonstrated by Galileo's experiments at the Leaning Tower of Pisa, where he showed that heavy and light objects hit the ground simultaneously when dropped from the same height.
In the context of the exercise, the thief and the box he carries are in free fall, indicating that the only force acting on them is gravity. As they descend, their speed increases due to gravitational acceleration until they land.
A remarkable aspect of free fall is that all objects, regardless of their masses, fall with the same acceleration when no other forces are present. This was famously demonstrated by Galileo's experiments at the Leaning Tower of Pisa, where he showed that heavy and light objects hit the ground simultaneously when dropped from the same height.
In the context of the exercise, the thief and the box he carries are in free fall, indicating that the only force acting on them is gravity. As they descend, their speed increases due to gravitational acceleration until they land.
The Force of Gravity
Gravity is a fundamental force that attracts two bodies towards each other, and in most practical cases, it is the force that gives weight to physical objects. The strength of this force depends on the masses of the two objects and the distance between them.
For any object on Earth, gravity acts towards the Earth's center, and this force produces an acceleration of 9.8 m/s². The weight of an object, which is the force exerted by gravity, can be described using the formula:
For any object on Earth, gravity acts towards the Earth's center, and this force produces an acceleration of 9.8 m/s². The weight of an object, which is the force exerted by gravity, can be described using the formula:
- Weight (\( W \)) = mass (\( m \)) × gravitational acceleration (\( g \))
Explaining Normal Force
The normal force is the supportive force exerted by a surface to keep an object resting on it from falling under the force of gravity. In everyday situations, the normal force is what balances the weight of an object, preventing it from accelerating downward.
When an object is placed on a surface, such as a table or the ground, the normal force acts perpendicular to the contact surface to counterbalance the weight of the object. This is why you don't sink into the ground while standing or sitting.
During free fall, however, the condition is unique. The thief experiences no normal force because there is no surface providing support while in the air, resulting in zero apparent weight. This absence of a normal force is why objects, like the thief and his box, feel 'weightless' until they touch the ground.
When an object is placed on a surface, such as a table or the ground, the normal force acts perpendicular to the contact surface to counterbalance the weight of the object. This is why you don't sink into the ground while standing or sitting.
During free fall, however, the condition is unique. The thief experiences no normal force because there is no surface providing support while in the air, resulting in zero apparent weight. This absence of a normal force is why objects, like the thief and his box, feel 'weightless' until they touch the ground.
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