Chapter 2: Newton's First Law Of Motion, Inertia

When the man stands at rest on two bathroom scales, his weight is distributed evenly over both scales. This means that each scale is supporting half of his weight. Since his weight is 800 N, each scale would read half of that, which is 400 N. Therefore, the correct answer is 400 N.

According to Newton's law of inertia, an object in motion will continue moving in a straight line at a constant speed unless acted upon by an external force. In the case of a railroad train, there are always forces that oppose its motion, such as friction between the wheels and the tracks, air resistance, and the force required to overcome the train's own weight. These opposing forces eventually bring the train to a stop, even if its engine is turned off. Therefore, we never observe a railroad train in motion forever because there are always forces that act against its motion.

Galileo relied on experimentation in explaining nature. Unlike Aristotle who relied solely on logic, Galileo believed that the best way to understand the natural world was through conducting experiments and observing the results. Through his experiments, Galileo was able to challenge traditional beliefs and develop new theories about motion, gravity, and the behavior of objects. His emphasis on experimentation revolutionized the scientific method and laid the foundation for modern physics.

Inertia is the concept that most explains why the engine does not come to an abrupt stop when an automobile runs out of fuel while driving. Inertia is the tendency of an object to resist changes in its state of motion. In this case, the moving car has inertia, so even when the engine stops, the car will continue to move forward due to its momentum. It will gradually slow down and come to a stop as the frictional forces and resistance from the road gradually bring it to a halt.

When a rock is whirled at the end of a string, it follows a circular path due to the tension in the string that keeps it in that path. However, if the string breaks, there is no longer any force acting on the rock to keep it in a circular path. As a result, the rock will continue moving in a straight line according to Newton's first law of motion, which states that an object in motion will continue in a straight line at a constant speed unless acted upon by an external force. Therefore, the tendency of the rock when the string breaks is to follow a straight-line path.

The truck is moving at constant velocity, which means it is not accelerating or decelerating. When the rock is dropped from the midpoint of the ceiling, it will continue to move horizontally with the same velocity as the truck. Therefore, it will hit the floor directly below the midpoint of the ceiling, as there is no horizontal displacement.

The applied force needed to maintain a constant velocity is 10 N. This is because the force of friction on the sliding object is also 10 N. In order for the object to move at a constant velocity, the applied force must equal the force of friction. If the applied force is less than 10 N, the object would slow down and eventually come to a stop. If the applied force is more than 10 N, the object would accelerate and its velocity would change. Therefore, the applied force needed to maintain a constant velocity is 10 N.

When the paper is jerked quickly, it creates a sudden force on the milk carton. However, due to the milk carton's inertia, it tends to resist changes in its state of motion. Therefore, the milk carton remains in place and does not topple over. This demonstrates that the milk carton has inertia, which is the tendency of an object to resist changes in its motion. The other options are not applicable in this scenario.

When you stand at rest on a pair of bathroom scales, the readings on the scales will add up to equal your weight. This is because each scale measures the force exerted on it by your body, which is equal to your weight. Therefore, when you stand on both scales, the total force exerted on both scales will be equal to your weight.

When hanging from a pair of gym rings, the upward support forces of the rings add up to equal your weight. This is because the rings provide support in opposite directions, balancing the downward force of your weight. The upward support forces from each ring must be equal in magnitude but opposite in direction in order to keep you suspended. Therefore, when combined, these forces add up to equal your weight.

The horizontal speed of the package just before it hits the ground is about 30 m/s because neglecting air resistance means that there are no external forces acting on the package horizontally. Therefore, the package will continue to move with the same horizontal velocity as the truck, which is 30 m/s.

If no external forces are acting on a moving object, it will continue moving at the same velocity. This is because velocity is a vector quantity that includes both speed and direction. When there are no external forces acting on an object, there is no net force to change its speed or direction. Therefore, the object will continue moving in a straight line with the same velocity it had before.

When a rocket ship runs out of fuel, it no longer accelerates. This is because acceleration requires a force to be applied to an object, and in the absence of fuel, there is no force to propel the rocket forward. Without acceleration, the rocket will continue to move at a constant velocity or gradually slow down due to external forces like gravity or air resistance. However, it will not experience any further acceleration.

An object in mechanical equilibrium is one that is either at rest, moving with constant velocity, or experiencing no acceleration. This means that the net force acting on the object is zero, resulting in a balanced state where there is no change in its motion. Therefore, all of the given options are correct as they describe different scenarios in which an object can be in mechanical equilibrium.

The friction force between the tree and the bear is 3000 N. This is because the bear is sliding down at a constant velocity, which means that the net force acting on it is zero. Since the bear is moving downwards, the friction force must be equal in magnitude and opposite in direction to the force of gravity acting on the bear. The force of gravity on the bear can be calculated using the formula F = m*g, where m is the mass of the bear (300 kg) and g is the acceleration due to gravity (approximately 9.8 m/s^2). Therefore, the force of gravity on the bear is 300 kg * 9.8 m/s^2 = 2940 N. Since the friction force must be equal to this force, the friction force is 3000 N.

Galileo's use of inclined planes allowed him to slow down the acceleration of free fall. By using inclined planes, Galileo was able to reduce the steepness of the descent and increase the distance traveled, thereby slowing down the rate at which objects accelerated during free fall. This allowed him to study and measure the effects of gravity more accurately, leading to his groundbreaking insights into the laws of motion and the concept of acceleration.

Galileo was the scientist who first introduced the concept of inertia. He conducted experiments to study the motion of objects and observed that objects tend to stay at rest or in motion unless acted upon by an external force. This concept contradicted Aristotle's belief that objects naturally come to rest. Galileo's work laid the foundation for Newton's laws of motion and revolutionized the understanding of motion and inertia.

Galileo's interpretation of motion differed from Aristotle's in that Galileo emphasized time rates. This means that Galileo focused on the concept of measuring how quickly an object's motion changes over time, rather than just describing the object's overall distance or position. Galileo's emphasis on time rates allowed for a more precise understanding of motion and laid the foundation for the development of modern physics.