Motion along a Straight Line problem

In summary, the problem involves a hiker observing a boulder falling from a distant cliff and noting that it takes 1.30 seconds for the boulder to fall the last third of the way to the ground. The hiker has calculated the last third of the distance to be 8.281 meters using the formula y=(1/2)(a)(t^2) with a=gravity=9.8 meters per second. However, the hiker is unsure how to find the total distance of the cliff because the boulder is accelerating throughout the entire distance. The conversation then discusses using the velocity at the beginning and end of the last third to calculate u and v in terms of distance fallen.
  • #1
ledhead86
59
0
Motion along a Straight Line problem !PLEASE HELP!

An alert hiker sees a boulder fall from the top of a distant cliff and notes that it takes 1.30 s for the boulder to fall the last third of the way to the ground. You may ignore air resistance.

I have calculated the last 1/3 of the distance to be 8.281 m by the formula y=(1/2)(a)(t^2) where a=gravity=9.8 meters per second.
However to find the total distance of the cliff, I can't just multiply the distance of the last third times 3 because the boulder is accelerating throughout the entire distance, so how do I find the totatl distance?
 
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  • #2
For some reaosn I'm stumped right now, but I can tell you that
I have calculated the last 1/3 of the distance to be 8.281 m by the formula y=(1/2)(a)(t^2) where a=gravity=9.8 meters per second.
doesn't work because
because the boulder is accelerating throughout the entire distance
applies to this part of the problem too.
 
  • #3
You only have distance moved and time to work with. And gravity of course.

Let u be the velocity at beginning of last third
Let v be the velocity when stricking the ground.

Calculate u in terms of distance fallen
Calculate v in terms of distance fallen

The distance moved has been used. Can you now relate u and v in terms of t ?
 

1. What is motion along a straight line?

Motion along a straight line refers to the movement of an object in a single direction without any changes in its direction or orientation.

2. What are the key principles of motion along a straight line?

The key principles of motion along a straight line are displacement, velocity, and acceleration. Displacement is the distance an object has moved from its starting point, velocity is the rate of change of an object's displacement, and acceleration is the rate of change of an object's velocity.

3. How is motion along a straight line represented graphically?

Motion along a straight line can be represented graphically with a position-time graph, where the vertical axis represents position or displacement and the horizontal axis represents time. The slope of the graph represents the velocity of the object.

4. What is the difference between average and instantaneous velocity?

Average velocity is the total displacement of an object divided by the total time taken, while instantaneous velocity is the velocity of an object at a specific moment in time. Average velocity gives an overall picture of an object's motion, while instantaneous velocity shows how the object is moving at a specific point in time.

5. How does acceleration affect motion along a straight line?

Acceleration can change the velocity of an object, either by increasing or decreasing it. If an object is accelerating, its velocity is changing, and if the acceleration is constant, the velocity will change at a constant rate. Objects with positive acceleration will speed up, while objects with negative acceleration will slow down.

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