How Does the Speedometer Reading Change as an Object Falls?

[missie]

Let's say a rock had a speedometer on it so that you could measure how fast it was going at any moment. By how much would the speed reading on the speedometer increase with each second that it fell?

what is your answer to this question?

can you explain?

i also learned today that g = 9.8 for most things right?

 

[PhanthomJay]

Let's say a rock had a speedometer on it so that you could measure how fast it was going at any moment. By how much would the speed reading on the speedometer increase with each second that it fell?

what is your answer to this question?

can you explain?

i also learned today that g = 9.8 m/sec^2[/color] [/color]for most things right?

g, the acceleration of gravity, applies at or near the Earth's surface, for all objects. What did you learn about the relationship between speed, acceleration, and time?

 

[missie]

that no matter what time or how long it stays at g = 9.8 m/s

 

[PhanthomJay]

that no matter what time or how long it stays at g = 9.8 m/s

What I mean is, I know you have studied the kinematic equations of motion for free fall, you know, the ones like vf = vo + ?

 

[missie]

vf = vo + at ? and the teacher said for free fall it's vf = gt

 

[PhanthomJay]

vf = vo + at ? and the teacher said for free fall it's vf = gt

well, that's if vo is zero (if it starts from rest). In general, vf=vo +gt, or rearranging, vf-vo =gt, that is , \Delta v = gt. So what's the velocity change each second? Don't forget units.

 

[missie]

how will i know the velocity change every second when i can't solve that because it doesn't tell time. It tells me to answer with words and that its not a math problem.

 

[Mattowander]

Think about what is actually happening. When we say that g = 9.8 m/s^2 , what is that saying? Acceleration refers to the change in velocity over time.

An object in free fall starting from an initial speed of zero falls at a velocity of 9.8 m/s after ONE second. How fast do you think it's going after two seconds?

 

[missie]

should it be 9.8 x 2 = 19.6m/s at 2 second?

 

[Mattowander]

You're one the right track yes.

What the acceleration 9.8m/s^2 means is that every second, the velocity increases by 9.8m/s. Now do you understand how that works?

 

[missie]

yes i understand now thank you so much ;]

 

[Mattowander]

No problem :)