Gravitation

Same acceleration regardless of their mass

Step 1: From Newton's law of gravitation, F = GMm/R² and from Newton's second law, F = ma. Step 2: Combining these, we get a = GM/R², which shows acceleration is independent of object's mass 'm'. Step 3: This means a feather and a hammer would fall at the same rate in vacuum (no air resistance). Step 4: Galileo demonstrated this principle, and it's fundamental to understanding gravity. Options 2 and 3 are wrong because acceleration doesn't depend on mass or size. Option 4 is wrong because gravity always produces acceleration.

The gravitational force acting on the object

Step 1: Weight is defined as the gravitational force that Earth exerts on an object. Step 2: It is calculated using the formula W = mg, where m is mass and g is acceleration due to gravity. Step 3: Weight is measured in Newtons (N), which is a unit of force. Step 4: Unlike mass, weight can change with location (different planets have different g values). Mass is a measure of matter, not weight. Volume and density are physical properties but don't represent the gravitational force acting on an object.

The 50 cm mark

Step 1: Center of gravity is the point where the entire weight of an object appears to be concentrated. Step 2: For uniform objects with regular shapes, the center of gravity is at the geometric center. Step 3: A meter scale is 100 cm long, so its center is at 100/2 = 50 cm. Step 4: This is where the scale would balance perfectly on a fulcrum. Other options represent either end points or quarter points, which would not be the balance point for a uniform meter scale.

Zero

Step 1: Weight is defined as the force an object exerts against its support. Step 2: During free fall, there is no support force acting on the object. Step 3: Although gravitational force still acts on the object, there's no reaction force from a support. Step 4: This creates the sensation of weightlessness, like astronauts experience in space. The object still has mass and gravity acts on it, but its apparent weight (what a scale would read) becomes zero because both the object and scale fall together.