GERAK VERTIKAL ( Gerak Jatuh Bebas, Gerak Vertikal Ke atas dan ke bawah)

Summary

This video explains vertical motion in physics, covering free fall, vertical motion upwards, and vertical motion downwards. It highlights key differences, such as initial velocity presence and motion direction relative to gravity. Using clear examples like a falling fruit, a stone thrown into a ravine, and a ball thrown upwards, the video demonstrates how to apply the three main equations of motion for vertical scenarios. It walks through calculating maximum height, time to reach the highest point, and final speed, including practical exercises like determining the height of a building from free fall time and the speed of a falling pen. Concepts are simplified for clear understanding.

Takeaways

• 😀 Vertical motion occurs along the y-axis, either upwards or downwards, under the influence of gravity.
• 😀 There are three types of vertical motion: free fall, vertical motion upwards, and vertical motion downwards.
• 😀 Free fall motion has no initial velocity, e.g., a fruit falling from a tree without external forces.
• 😀 Vertical motion downwards has an initial velocity, e.g., a stone thrown downward by a child.
• 😀 Vertical motion upwards occurs against gravity and always starts with an initial velocity.
• 😀 At the highest point of upward vertical motion, the object's velocity becomes zero.
• 😀 GLBB formulas can be adapted for vertical motion by replacing acceleration with the acceleration due to gravity (G) and distance with height.
• 😀 Maximum height in upward vertical motion can be calculated using the formula v² = u² - 2gh, with final velocity at the top being zero.
• 😀 Time to reach the maximum height can be found using t = (v - u)/(-G) or directly dividing initial velocity by gravity.
• 😀 Free fall problems can use the formula h = 0.5 * G * t² to calculate height, and final speed when hitting the ground can be found with v = G * t.
• 😀 Understanding initial velocity is key to distinguishing between free fall and downward vertical motion.
• 😀 In practical examples, calculations assume gravity as 10 m/s² for simplicity.

Q & A

What are the three types of vertical motion discussed in the video?

The three types are: Free Fall Motion (GB), Vertical Motion Upwards (GCA), and Vertical Motion Downwards (GVB).

How is Free Fall Motion different from Vertical Motion Downwards?

Free Fall Motion has no initial velocity and occurs naturally under gravity, like a fruit falling from a tree. Vertical Motion Downwards has an initial velocity provided by an external force, such as throwing a stone downward.

In vertical motion upwards, what happens to the object's speed at the highest point?

At the highest point, the object's speed becomes zero because it has overcome gravity and is about to start descending.

What is the general formula for velocity in vertical motion?

The velocity formula is v = u ± g t, where 'u' is initial velocity, 'g' is gravity, 't' is time, and the sign depends on the direction relative to gravity (minus for upwards, plus for downwards).

How do you calculate the maximum height of an object thrown vertically upwards?

Use the formula v^2 = u^2 - 2 g h, where v = 0 at maximum height. Solve for h: h = u^2 / (2 g).

If a ball is thrown upwards at 10 m/s with gravity 10 m/s², what is its maximum height?

Using h = u^2 / (2 g): h = 10^2 / (2 * 10) = 100 / 20 = 5 meters.

How do you calculate the time it takes for an object to reach the highest point in vertical motion upwards?

Use the formula t = u / g, where u is the initial velocity and g is the acceleration due to gravity.

A pen is dropped from a building with no initial speed and falls for 5 seconds with gravity 10 m/s². How high is the building?

Using h = 1/2 g t^2: h = 0.5 * 10 * 5^2 = 0.5 * 10 * 25 = 125 meters.

What is the speed of the pen when it hits the ground after falling for 5 seconds?

Using v = u + g t: v = 0 + 10 * 5 = 50 m/s.

How does the direction of motion affect the choice of sign in vertical motion formulas?

If the motion is in the same direction as gravity (downwards), use a plus sign. If the motion is against gravity (upwards), use a minus sign.

Why is the initial velocity zero in free fall motion but not in vertical motion downwards?

In free fall motion, the object starts from rest and moves only under gravity. In vertical motion downwards, the object is given an initial push or throw, providing it with an initial velocity.

Which formula is most suitable to calculate height when time is given in free fall motion?

The formula h = u t + 1/2 g t^2 is suitable. If u = 0, it simplifies to h = 1/2 g t^2.