Chapter 29: Your Friend Says That Inertia Is A Force That Ke

Chapter 29your Friend Says That Inertia Is A Force That Keeps Things

Can an object reverse its direction of travel while maintaining a constant acceleration? If so, give an example. If not, provide an explanation.

What weight change occurs when your mass increases by 2kg?

A race car travels along a race way at a constant velocity of 200km/h. What horizontal net force acts on the car?

Consider a baseball player batting a ball: (a) identify the action-reaction pairs when the ball is being hit, and (b) while the ball is in flight.

Paper For Above instruction

Inertia is often misunderstood as a force that keeps objects at rest or in uniform motion. However, scientifically, inertia is a property of matter that resists changes in its state of motion. It is not a force but rather an object's tendency to maintain its current state, whether at rest or moving uniformly. This resistance is described quantitatively by mass, with larger masses exhibiting greater inertia. In classical Newtonian mechanics, forces are responsible for changing an object's motion, while inertia provides the resistance to such changes (Halliday, Resnick, & Walker, 2014).

Regarding the reversal of an object’s direction while maintaining constant acceleration: it is indeed possible. Acceleration is a vector quantity with both magnitude and direction. An object can experience a constant magnitude of acceleration while changing direction, such as uniform circular motion where the acceleration points towards the center of the circle at all times. An example is a car turning around a curve at a constant speed; even though the speed remains constant, the continuous change in direction results in a centripetal acceleration directed inward toward the center of the curve (Serway & Jewett, 2018). Therefore, an object can reverse its direction if the acceleration vector continuously points opposite to its initial velocity, as observed in projectile motion when reaching the peak of its trajectory, where the velocity momentarily becomes zero, then reverses direction under gravity’s influence (Tipler & Mosca, 2008).

If a person's mass increases by 2kg, their weight increases by the product of mass and gravitational acceleration. Assuming standard gravity \( g \approx 9.81\, \text{m/s}^2 \), the increase in weight is calculated as follows: \(\Delta W = \Delta m \times g = 2\, \text{kg} \times 9.81\, \text{m/s}^2 = 19.62\, \text{N}\). Therefore, an increase of 2kg in mass results in a weight increase of approximately 19.62 newtons (Hewitt, 2014).

For the race car traveling at a constant velocity of 200 km/h, the net force acting on it along the horizontal direction is zero. According to Newton’s first law, an object moving at constant velocity has zero net external force acting on it. Since velocity remains constant, the sum of all forces in the horizontal direction must cancel out, indicating a balanced force scenario where friction and air resistance are exactly countered by the engine's driving force (McCall, 2017).

In the case of a baseball being hit by a player: (a) the action-reaction pair involves the bat applying a force to the ball (action), and the ball applying an equal and opposite force to the bat (reaction). The forces are equal in magnitude and opposite in direction, as described by Newton's third law. (b) While the ball is in flight, the primary forces acting on it are gravity (downward force) and air resistance (drag). The action-reaction pair still exists between the ball and the bat during the hit, but during flight, the forces are external, with gravity pulling the ball downward and air resistance opposing its motion.

References

• Halliday, D., Resnick, R., & Walker, J. (2014). Fundamentals of Physics (10th ed.). Wiley.
• Hewitt, P. (2014). Conceptual Physics (12th ed.). Pearson.
• McCall, G. (2017). Physics for Engineers and Technicians. Pearson Education.
• Serway, R. A., & Jewett, J. W. (2018). Physics for Scientists and Engineers (9th ed.). Cengage Learning.
• Tipler, P. A., & Mosca, G. (2008). Physics for Scientists and Engineers. W. H. Freeman and Company.