# Suvat Question - seemingly too little info

• TicTac2
In summary, the conversation is about a question regarding throwing a ball vertically into the air and finding its initial velocity, maximum height, and speed at impact. The correct formula to use is \Delta x = v_{i}t + \frac{1}{2}at^{2} and it is important to consider the sign of displacement, which in this case is negative as the ball finishes lower than its initial position.
TicTac2
Hi all,
I am new here with probably what is a very simple question for most. I hope I am posting this in the right place. The question is:

A ball is thrown vertically into the air, and leaves the thrower's hand when it is 1.6m above the ground. It hits the ground 3.1s later.

Assume acceleration as 9.8, and assume no air resistance.

You have to find out everything really - initial velociy, maximum hieght, and speed at impact.

It seems quite simple but I can't get anyway.

I tried assuming displacement as 1.6m and a as 9.8, and did 1.6m=3.1t+4.9t^2. I got the answer 14.7m/s but you can't do that can you as a changes from + to -. Our teacher reckons the answer is closer to 12 but isn't really sure.

I also tried some simultaneous questions but ended up with stuff like 4.9t^2=4.9t^2

So what is the correct method?

Thanks very much

Welcome to the Forums,

Your almost there with your first method, note that the ball finishes lower than it's initial position. What does this tell you about the sign of the displacement? Also note that the correct formula is;

$$\Delta x = v_{i}t + \frac{1}{2}at^{2}$$

It may have been a typo in your above post but your equation seemed incorrect.

Hootenanny said:
Welcome to the Forums,

Your almost there with your first method, note that the ball finishes lower than it's initial position. What does this tell you about the sign of the displacement? Also note that the correct formula is;

$$\Delta x = v_{i}t + \frac{1}{2}at^{2}$$

It may have been a typo in your above post but your equation seemed incorrect.

I think I did have the equation correct I just shortened 1/2xa to 4.9.

The negative displacement is the mistake I'm making.

Thanks very much for the info!

TicTac2 said:
I tried assuming displacement as 1.6m and a as 9.8, and did 1.6m=3.1t+4.9t^2.
This should be vit or 3.1vi as 3.1 is the time t. A minor typing error though as it looks like you worked it out correctly.

My pleasure

## What is a "Suvat Question"?

A "Suvat Question" is a type of physics problem that involves using the Suvat equations to solve for the unknown variables of motion (displacement, initial velocity, final velocity, acceleration, and time).

## Why does a "Suvat Question" seem to have too little information?

Suvat questions often seem to have too little information because they typically only provide a few of the five variables needed to solve the problem. However, with the use of the Suvat equations and some algebraic manipulation, the missing variables can be calculated.

## What are the Suvat equations?

The Suvat equations are five equations that relate the five variables of motion (displacement, initial velocity, final velocity, acceleration, and time). They are:

• s = ut + 1/2at^2
• v = u + at
• v^2 = u^2 + 2as
• s = (u + v)/2 * t
• u = (v + u)/2 * t

## How do I solve a "Suvat Question"?

To solve a "Suvat Question", you must first identify which variables are given and which are unknown. Then, you can use the appropriate Suvat equation(s) to manipulate and solve for the unknown variable(s). It is important to remember to use consistent units and pay attention to the direction of motion.

## Are there any tips for solving "Suvat Questions"?

Yes, some tips for solving "Suvat Questions" include:

• Draw a diagram to visualize the problem and label the known and unknown variables.
• Use the most appropriate Suvat equation(s) based on the given information.
• Be consistent with units and pay attention to the direction of motion.
• Check your answer by plugging it back into the original equation or using a different equation.
• Practice and familiarize yourself with the Suvat equations and their applications.

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