Belajar Fisika

# Question and Discussion of Physics about Vertical Movement

Vertical movement is divided into three types, namely free fall, vertical movement downward, and vertical movement upward. Below are some examples of questions and discussions about vertical movement.

First question: A object is falling freely from a height of 80 m. Calculate the time required for the object to reach the ground if gravity is 10 m/s2!

Solution:

From the question, we know that the object is experiencing free fall. For an object experiencing free fall, it’s important to remember that its initial velocity (v0) is zero. The formula used is

Next, let’s write down the physical quantities that are known in the question so that we can find out the time required for the object to fall freely from a height of 80 meters.

Currently, we have the values of the physical quantities listed in the formula, now let’s find out the time required for the object to fall freely from a height of 80 meters to reach the ground! The formula that we have is

So, the time required for the object to fall freely from a height of 80 meters to reach the ground is 4 seconds.

Second question: A pebble is thrown into a dry well with an initial velocity of 5 m/s. If the pebble hits the bottom of the well after 2 seconds, then the speed of the pebble when it hits the bottom of the well and the depth of the well are respectively… (g = 10m/s^2)?

Solution: From the question, we know that the object is experiencing vertical movement downward. The formula used to calculate the velocity of the pebble when it reaches the bottom of the well is

First, let’s calculate the speed of the pebble when it reaches the bottom of the well first:

Second, let’s calculate the depth of the well:

So, the speed of the pebble when it hits the bottom of the well is 25 m/s and the depth of the well is 30 m.

Third question: A mango is located at a height of 20 meters. Calculate the minimum throwing speed of a stone so that the mango will be hit by the stone throw is…

Solution: From the question, we know that the object is experiencing vertical movement upward, which is the case of throwing a stone at a mango. From the question, we know that the final velocity (vt^2) of the stone is zero because it hits the mango and falls to the ground. Then, the direction of the stone’s acceleration used to throw the mango is opposite to the direction of gravity, so its gravity value is negative.

The formula used to calculate the minimum throwing speed of a stone so that the mango will be hit by the stone throw is:

So, the minimum throwing speed for the stone to hit the mango is 20 m/s.

Question Four: A ball is thrown vertically upwards with an initial velocity of 40 m/s. The height of the ball at t = 3 seconds after it was thrown is …. (g = 10 m/s^2)

Solution: From the problem statement, it is clear that this problem is about vertical motion upwards. The problem we need to solve is the height achieved by the ball at the third second after it is thrown vertically upwards. It should be noted that what we are looking for is the magnitude of the height achieved by the ball at the third second after it is thrown vertically upwards, not the maximum height achieved by the ball. Furthermore, the direction of the ball’s acceleration is opposite to the direction of gravity, so its gravity is negative. The formula used is

So,the height of the ball at t = 3 seconds after it was thrown with an initial velocity of 40 m/s is 75 meters.

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#### Salverius Jagom

Guru Fisika Di SMA Negeri 2 Nubatukan