Help Needed for Physics Problem: Falling Objects and One Number

In summary, the question is asking for how long it took for the object to fall from 300m to the ground. You should solve for time, after which you can solve for velocity.
  • #1
mystry4
14
0
I have just started a Physics class after having been away from algebra and equations for quite awhile. This is probably a very silly, elemenetary question, but here goes:
With falling objects, I understand that g=10m/s2
and I know the formula that is used, however, I am working with only one number (the height of 300m) to find how long and how fast,and I can't figure out how to plug one number into the formula.
I think that the t=30.0s and v=300m/s and if that is correct I don't know how to do the work to get there.
I know this is easy, but I am missing something.
Can anyone help?
Thank you.
 
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  • #2
Does the equation y=y_0 +v_0t+1/2at^2 ring a bell? You are probably supposed to make some assumptions here. Assume you are starting off with zero initial velocity. Choose a coordinate system for the problem and assign the appropriate values for the initial and final positions. From that find time, after finding time find velocity
 
  • #3
Perhaps it would help if you wrote out the complete question for us.

Generally, to solve these sort of constant acceleration problems, there are five different variables that can come into play. These are acceleration, initial velocity, final velocity, elapsed time, and elapsed distance. If you are learning about kinematics, you should have learned several equations that relate at some of the variables together.

Fill out the following chart with the information given. The first thing you should do is figure out what the question is asking. For example, for "how long?" you are looking for elapsed time. So put a question mark (?) next to the delta t. Then fill in the information that you know. For example, since this is free fall, you would put 10m/s^2 next to "a". Do you know how fast the object was moving when it first starts (v-initial)? Do you know how fast the object was moving at the end (v-final)? Do you know how much distance elapsed (delta x)?

[tex]a=[/tex]

[tex]v_i=[/tex]

[tex]v_f=[/tex]

[tex]\Delta t=[/tex]

[tex]\Delta x=[/tex]

Once you've filled in as much information as possible, you can put an X next to the variables to which you have no information. For example, if you're solving for the time but you have no information on how fast it was when it reached the ground, then put an X next to v_f.

Then go through your equations and find the one that has every variable except the one that you put an X through. You should have several equations to choose from, each with one of the five variables missing. Then take that equation and fill in your known information and solve for the one variable.

Good luck!
 
  • #4
Thank you! That helped me solve the problem!
 

What is the problem about falling objects and one number?

The problem is about finding the value of one unknown number in a physics equation involving falling objects. This could involve variables such as time, distance, velocity, or acceleration.

What is the formula for calculating the motion of falling objects?

The formula for calculating the motion of falling objects is d = 1/2 * a * t^2, where d is the distance, a is the acceleration due to gravity, and t is the time.

How do I solve a falling object physics problem?

To solve a falling object physics problem, follow these steps:
1. Identify the known and unknown variables.
2. Use the formula d = 1/2 * a * t^2 to set up an equation.
3. Rearrange the equation to solve for the unknown variable.
4. Substitute the known variables into the equation.
5. Solve for the unknown variable to get the final answer.

What units should be used in a falling object physics problem?

In a falling object physics problem, the units used should be consistent. The distance should be in meters (m), the acceleration should be in meters per second squared (m/s^2), and the time should be in seconds (s).

What are some common mistakes to avoid when solving falling object physics problems?

Common mistakes to avoid when solving falling object physics problems include using incorrect units, not considering the direction of motion (positive or negative), and not rearranging the equation correctly to solve for the unknown variable. It is also important to double check calculations and make sure all steps are clearly shown.

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