QUEDA LIVRE e LANÇAMENTO VERTICAL - [Física do ZERO]

Summary

This video explains free fall and vertical launch movements in physics. It covers key concepts like acceleration due to gravity, which is approximately 10 m/s² on Earth. The presenter distinguishes between free fall (when an object is dropped) and vertical launch (when an object is thrown upwards or downwards). Using equations of uniformly accelerated motion, examples are provided, such as a flowerpot falling from a height and a ball thrown upwards. The presenter emphasizes the importance of understanding acceleration's direction, with gravity always acting downwards, and demonstrates calculations for time and height in different scenarios.

Takeaways

• 😀 Free fall occurs when an object is at rest and then simply allowed to fall due to gravity, whereas vertical launch involves throwing an object upwards or downwards.
• 😀 Both free fall and vertical launch are examples of uniformly accelerated motion (UAM), where acceleration is constant throughout the motion.
• 😀 The acceleration due to gravity is always downward and is represented by 'g'. On Earth, its value is approximately 10 m/s², but it varies on other planets or moons.
• 😀 In exercises, the value of gravitational acceleration is typically provided, so you don't need to memorize it for different celestial bodies.
• 😀 For easier problem-solving, assume the positive direction is upwards in vertical motion and place the origin (zero point) at the lowest point.
• 😀 When the motion involves gravity, the acceleration is taken as negative (−g) because gravity always acts downward, against the upward direction.
• 😀 The three main kinematic equations used in UAM are: s = s₀ + v₀t + (1/2)at², v = v₀ + at, and v² = v₀² + 2a(s - s₀).
• 😀 In free fall or vertical launch problems, remember that acceleration due to gravity is often negative (−10 m/s²) when using upward as positive.
• 😀 In the example of an object falling from a height of 20 meters, the time it takes to hit the ground can be calculated using the kinematic equations, resulting in 2 seconds.
• 😀 In vertical launch problems, such as throwing an object upwards, the maximum height reached is determined when the object's velocity becomes zero, and this can be calculated using the kinematic equations.

Q & A

What is the main difference between free fall and vertical launch?

The key difference is that in free fall, an object is at rest and simply drops under gravity, whereas in a vertical launch, an object is thrown upwards or downwards with initial velocity.

Why are free fall and vertical launch considered uniformly accelerated motion?

Both free fall and vertical launch involve constant acceleration due to gravity. This constant acceleration makes these movements uniformly accelerated.

What is the acceleration due to gravity on Earth?

On Earth, the acceleration due to gravity is approximately 10 meters per second squared (m/s²), though it can be more precisely stated as 9.8 m/s².

How should we define the positive direction in vertical motion problems?

The positive direction should be defined as upward in vertical motion problems, as it simplifies the understanding and calculation of displacement and velocity.

Why is the acceleration due to gravity considered negative in vertical motion problems?

Gravity always acts downward, opposite to the defined positive direction (upward). Therefore, in vertical motion problems, gravity is assigned a negative value to reflect its downward force.

What are the standard equations used in uniformly accelerated motion?

The key equations are: 1) s = s₀ + v₀t + (at²)/2, 2) v = v₀ + at, and 3) v² = v₀² + 2as, where s is displacement, v is velocity, v₀ is initial velocity, a is acceleration, and t is time.

What would be the acceleration value in free fall near Earth's surface?

In free fall near Earth's surface, the acceleration is typically 10 m/s², representing the gravitational pull of the Earth.

How can we determine the time it takes for an object in free fall to reach the ground?

We can use the uniformly accelerated motion equation: s = s₀ + v₀t + (at²)/2. By substituting the known values (initial velocity, acceleration due to gravity, and initial height), we can solve for time.

Why is it important to define the positive direction as upward in vertical motion problems?

Defining the positive direction as upward simplifies the problem-solving process, as it aligns with common conventions in physics, making calculations more intuitive.

In the example where a flowerpot falls from a 20-meter high window, how long does it take to reach the ground?

Using the equation s = s₀ + v₀t + (at²)/2, where the initial velocity (v₀) is 0, the height (s₀) is 20 meters, and the acceleration is -10 m/s² (gravity), the time (t) comes out to be 2 seconds.