# Simple Laws of motion question

• faamfwvame
In summary, during a science experiment, an object weighing roughly 550 grams was launched vertically and remained airborne for approximately 4.5 seconds. Using the formula v = v_0 - gt, and assuming negligible air resistance, it can be calculated that the object was launched at a speed of 49.5 miles per hour and reached a peak height of 36.7875 meters before falling to the ground. However, as the individual conducting the experiment has no experience with physics, they are unsure of the accuracy of these results.
faamfwvame
A friend and I were conducting a science experiment, where an object weighing roughly 550 grams was launched vertically, and after examining the video footage, was airborne for aproximatly 4.5 secconds. Having never studied physics before, I was curious if you could calculate the launch speed and or peak height from this information.

Any help would be highly appreciated.

Last edited:
Assuming negligible air resistence, which is approximatelytrue if the object is a ball made of a dense material, the velocity of a body moving against gravity is $$v = v_0 - gt$$
At the top of the trajectory the velocity is 0 and the time is half the total time.

I don't really understand that sorry, but according to Wikipedia, a stationary object's speed increases by 9.81 metres per second as it falls. and since my object was falling for 4.5/2, 2.25 secconds, I figured the peak hieght would be 9.81 + (9.81x2) + (9.81x3)/4 which equals 36.7875 metres, which, having seen the object, sounds about right. And 9.81 being approximatly 22 miles per hour, I guessed the speed it was traveling when it hit the ground and indeed the speed it was launched at would be 22 x 2.25 which is 49.5 miles per hour.
However, having no expirience with physics, I am hesitant to trust these results. Could anyone confirm or correct this?

faamfwvame said:
I don't really understand that sorry, but according to Wikipedia, a stationary object's speed increases by 9.81 metres per second as it falls. and since my object was falling for 4.5/2, 2.25 secconds, I figured the peak hieght would be 9.81 + (9.81x2) + (9.81x3)/4 which equals 36.7875 metres, which, having seen the object, sounds about right. And 9.81 being approximatly 22 miles per hour, I guessed the speed it was traveling when it hit the ground and indeed the speed it was launched at would be 22 x 2.25 which is 49.5 miles per hour.
However, having no expirience with physics, I am hesitant to trust these results. Could anyone confirm or correct this?
I don't understand the calculations you made. The initial and final velocities are equal in absolute values.
$$v_0 = 9.81*2.25 = 22m/s = 11.4 mph$$
The maximum heogth will be
$$h = v_0*t - \frac{1}{2]g*t^2 = 24.8m$$

## 1. What are the three laws of motion?

The three laws of motion, also known as Newton's laws of motion, are basic principles that explain the behavior of objects in motion. They are:

• First Law: An object at rest stays at rest and an object in motion stays in motion with a constant velocity unless acted upon by an unbalanced force.
• Second Law: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. This can be expressed as F=ma, where F is force, m is mass, and a is acceleration.
• Third Law: For every action, there is an equal and opposite reaction.

## 2. How do these laws apply to everyday situations?

These laws apply to everything in our daily lives, from the way a ball rolls down a hill to the way a car moves on the road. For example, the first law explains why objects stay in motion unless acted upon by a force, which is why a car will continue moving even after the engine is turned off. The second law explains why it takes more force to push a heavy object than a lighter one. And the third law explains why you feel a pushback when you push against a wall.

## 3. Who came up with the laws of motion?

The laws of motion were first described by English physicist and mathematician Sir Isaac Newton in his book "Philosophiæ Naturalis Principia Mathematica" in 1687. However, other scientists and philosophers had also observed and described similar principles before Newton, such as Galileo and Descartes.

## 4. Are there any exceptions to these laws?

While these laws are generally accepted as fundamental principles of physics, there are some situations where they may not apply. For example, at very high speeds or in extreme gravitational fields, the laws of motion may need to be modified to account for the effects of relativity. Additionally, in the quantum realm, the laws of motion may not apply in the same way as they do in the macroscopic world.

## 5. How are the laws of motion related to other branches of physics?

The laws of motion are closely related to other fundamental concepts in physics, such as force, energy, and momentum. They also form the basis for other laws and principles, such as the law of conservation of energy and the law of conservation of momentum. Understanding the laws of motion is essential for understanding the behavior of objects in motion and how they interact with each other.

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