What formula should I use to find velocity in a newtonian physics problem?

  • Thread starter amochang
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In summary, d/s is a halfway point in the calculation, and the final answer can be found from a velocity-time graph.
  • #1
amochang
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I'm a newbie to this subject, so forgive me if what I'm asking supposed to be common sense. :confused:

An airplane travels 280 m down the runway before taking off. If it starts from rest, moves with a constant acceleration, and becomes airborne in 8.00 s, what is its speed in m/s, when it takes off?

So, I think what is given is d=280m then t=8.00s and it is implied that it's initial velocity is 0. And what is asked is the speed or velocity...

Here's the thing. My friend keeps telling me that I should find first acceleration before speed, but I keep saying that I can simply just use d/s. Then, that conversation left me confused.

So, what formula should I really use?
 
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  • #2
You should think about how distance traveled by a plane and it's speed change with time when acceleration is constant. Then you'll be able to get answer from simultaneous equations.
 
  • #3
d/s will give you the average velocity over the displacement s. It won't tell you the final velocity. However, for constant acceleration there is a relationship between the average velocity and the final velocity after a given distance. Your textbook or class notes should have it.
 
  • #4
amochang said:
I'm a newbie to this subject, so forgive me if what I'm asking supposed to be common sense. :confused:

An airplane travels 280 m down the runway before taking off. If it starts from rest, moves with a constant acceleration, and becomes airborne in 8.00 s, what is its speed in m/s, when it takes off?

So, I think what is given is d=280m then t=8.00s and it is implied that it's initial velocity is 0. And what is asked is the speed or velocity...

Here's the thing. My friend keeps telling me that I should find first acceleration before speed, but I keep saying that I can simply just use d/s. Then, that conversation left me confused.

So, what formula should I really use?

it is possible to solve this problem by first finding the acceleration - as your friend says. Finding the acceleration is like a half-way point.

It is also possible to use d/s - but that also is a halfway point in the calculation, not the final answer.

You could even draw a velocity-time graph, and get the answer from that.
 
  • #5


I can understand your confusion about which formula to use to find the speed or velocity in this scenario. The formula you will need to use is v = u + at, where v is the final velocity, u is the initial velocity (which is 0 in this case), a is the acceleration, and t is the time. In this problem, you are given the distance (d), time (t), and initial velocity (u=0), so you can rearrange this formula to solve for the final velocity (v). The acceleration can be found by using the formula a = (v-u)/t, or in this case, a = d/t^2. This means that you can find the acceleration by dividing the distance (d) by the square of the time (t). Once you have found the acceleration, you can plug it back into the first formula to solve for the final velocity (v). I hope this helps clarify the steps you need to take to find the velocity in this problem. Keep in mind that in science, it is important to use the appropriate formulas and units to accurately solve a problem.
 

1. What is the definition of velocity?

Velocity is a measure of an object's speed and direction. It is a vector quantity, meaning it has both magnitude (speed) and direction.

2. How is velocity different from speed?

Velocity includes both speed and direction, while speed only measures how fast an object is moving. For example, a car going 50 miles per hour due north has a velocity of 50 miles per hour north, while a car going 50 miles per hour in a circle has a speed of 50 miles per hour but no velocity because it is constantly changing direction.

3. What is the formula for calculating velocity?

The formula for velocity is velocity = distance traveled / time taken. It is often represented as v = d/t, where v is velocity, d is distance, and t is time.

4. How is velocity measured?

Velocity is typically measured in units of distance per time, such as meters per second or miles per hour. It can be measured using tools such as speedometers, radar guns, or by calculating the change in position over a specific time interval.

5. What factors can affect an object's velocity?

An object's velocity can be affected by several factors, including acceleration, gravity, air resistance, and friction. Other factors that can affect velocity include the object's mass, the force applied to it, and the surface it is moving on.

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