Physics quiz problem

Physics Quiz problem #3

How far will an object, initially at rest, in free fall have traveled by the time it’s instantaneous velocity reaches 20 m/s?

* Ignore air resistance**Use gravity = 10 m/s2

The problem….

Step 1: Draw a picture

object

object

Vinitial is at rest, or Vinitial = 0 m/s

Vfinal = 20 m/s

Gravity accelerates object at 10m/s2

Step 2: Write down what you know

Vinitial = 0 m/s

Vfinal = 20 m/s Acceleration, or a = 10 m/s2

Step 3: Identify relationships we know

The problem asked us for distance so we know we’ll need to use

Unfortunately we don’t know either distance traveled or the time.

But!!

We were looking for….

We can find the time by using the relationship

But lets make it more user friendly

Don’t forget the other guys

We know acceleration and the change in velocity so…

Step 4: Fill in the numbers

Now that we know the time it takes is 2 seconds…

Step 4 continued…

Hopefully you noticed that the units worked out for when we solved for time and for distance….

So on to the next step~

The little things ~

Does the answer you found make sense?

This is where you consult your everyday experiences and make sure your answer can actually happen.

Step 5: Reality Check!

We solved the problem! Physics models everyday occurrences so your answer should make sense.

Congratulations!

The same object is in free fall once again. Ignoring air resistance, how far has an object at rest traveled from when it reaches a final instantaneous velocity of 30 m/s?

Check your work, the answer is 45 meters

Try this at home