Lesson 12: Summary on Vertical motion
- Terminal velocity is the maximum velocity a freely falling body can achieve when its acceleration becomes zero.
- This occurs because the upward drag force due to air resistance becomes equal to the downward gravitational force.
- Reaction time refers to the time taken by an individual to respond to a sudden event, like a driver applying brakes when a child appears on the road.
- The acceleration due to gravity, denoted as g, is a constant 9.8 m/s² on Earth’s surface and is responsible for the free fall of objects, where they move solely under the influence of gravity.
- Free fall examples include a stone dropped in a well, a ball in projectile motion, a spacecraft in orbit, and a fruit falling from a tree.
- In free fall, an object experiences a downward acceleration of 9.8 m/s², which remains constant whether the object is ascending or descending.
- The equations of motion for a freely falling body, starting from rest
- Free fall is characterized by motion under gravity’s influence without air resistance. However, in real-world scenarios, objects fall under the action of two forces: gravitational pull and drag force.
- Initially, the gravitational force exceeds the drag force, causing acceleration.
- As the object’s velocity increases, the drag force also increases until it equals the gravitational force.
- At this point, the object reaches terminal velocity and falls at a constant speed with zero acceleration.
- Terminal velocity depends on factors like the object’s shape, cross-sectional area, and the fluid’s nature.
- Galileo Galilei, contradicting Aristotle’s view that heavier objects fall faster, demonstrated that all objects in a vacuum fall at the same rate, regardless of their mass.
- He established that the distance covered in free fall is proportional to the square of the time taken.
- Galileo also made significant contributions to the study of motion on inclined planes, relative motion, and celestial observations, including the phases of Venus and the moons of Jupiter.
- Reaction time, crucial in scenarios like driving, is the interval between perceiving a hazard and initiating a response.
- It can be calculated using t=2dgt, where d is the distance and g is the acceleration due to gravity.
- Reaction distance, the distance traveled during reaction time, is given by
- Reaction Distance=Reaction Time ×Speed.