# Need Help Solving a Physics Problem? T=____?

• MHB
• cake81
In summary, we have a man throwing a tennis ball with an initial height of 2m and an initial velocity of 9m/s in the upwards direction. The ball is modeled as a particle moving freely under gravity with a constant acceleration of -10m/s. Using the kinematic equation, we can solve for the time it takes for the ball to hit the ground, which is approximately 2 seconds.
cake81
Hello! I need help with this question:
A tennis ball is thrown in the air by a man so that at the instant when the ball leaves his hand, the ball is 2m above the ground and is moving vertically upwards with speed9m/s^-1
The motion of the ball is modlledas that of a particle moving freely under gravityand the acceleration due to gravity is modeled as being of constant magnitude of 10 m/s^-1
The ball hits theground T seconds after leaving the hand
Using the model, find the value of T

I don't know how togo about solving this because I don't understand the part with the particle moving freely

Welcome, cake81! (Wave)

We are given an initial height of $y_0 = 2\,\text{m}$, an initial velocity of $v_0 = 9\, \text{m/s}$ in the upwards vertical direction, and an acceleration of $a = -10\,\text{m/s}$ (the acceleration vector faces downwards). Using the kinematic equation
$$y = y_0 + v_0 t + .5 at^2$$ with $y = 0$ we solve $0 = 2 + 9t + (.5)(10)t^2$, or $$5t^2 - 9t - 2 = 0$$ Can you take it from here?

Euge said:
Welcome, cake81! (Wave)

We are given an initial height of $y_0 = 2\,\text{m}$, an initial velocity of $v_0 = 9\, \text{m/s}$ in the upwards vertical direction, and an acceleration of $a = -10\,\text{m/s}$ (the acceleration vector faces downwards). Using the kinematic equation
$$y = y_0 + v_0 t + .5 at^2$$ with $y = 0$ we solve $0 = 2 + 9t + (.5)(10)t^2$, or $$5t^2 - 9t - 2 = 0$$ Can you take it from here?

thank you so much. i got 2, i only have to use the positive answer right?

Yes. Only the positive answer makes sense.

## 1. What is the formula for solving a physics problem?

The formula for solving a physics problem depends on the specific problem at hand. There are several basic equations in physics, such as Newton's laws of motion and the laws of thermodynamics, that can be used to solve a variety of problems. It is important to read the problem carefully and identify which formula is most relevant.

## 2. How do I know which variables to use in the formula?

To determine which variables to use in the formula, you should first identify what is given in the problem and what is being asked for. Then, you can use the appropriate formula and plug in the known values to solve for the unknown variable.

## 3. What units should I use when solving a physics problem?

The units used in physics problems are important and should be consistent throughout the calculation. It is recommended to use the SI (International System of Units) units, such as meters, kilograms, and seconds, as they are the standard units used in physics.

## 4. How do I check if my answer is correct?

To check if your answer is correct, you can use the unit analysis method. This involves checking if the units of your answer are the same as the units of the quantity being asked for in the problem. You can also double-check your calculation and ensure that you have used the correct formula and input values.

## 5. What should I do if I am still having trouble solving a physics problem?

If you are still having trouble solving a physics problem, it is recommended to seek help from a teacher or tutor. You can also try breaking the problem into smaller parts and tackling them one at a time. It is important to practice and understand the basic principles of physics in order to successfully solve problems.

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