Time to Fall 120m: Solving an SUVAT Problem with a Thrown Weight

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In summary, the conversation revolved around solving for the time it takes a dropped weight to fall 120m down a cliff and the time it would take if the weight was thrown downwards at 2.5m/s. The equation used was S = Ut+ .5At^2, and the quadratic formula was used to solve for t, with a resulting time of 4.7s.
  • #1
Rumplestiltskin
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Homework Statement


a) How much time does a dropped weight take to fall 120m down a cliff? (I answered this correctly as 4.9s -- √(s/0.5 x g).)
b) What would the time be (in question a) if the weight was thrown downwards at 2.5m/s?

Homework Equations


SUVAT

The Attempt at a Solution


None, apart from a mistaken rearrangement of s = ut + 0.5at^2.
 
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  • #2
I am not familiar with SUVAT, could you provide more detail?
In your equation S = Ut+ .5At^2, the only thing that changes from your first problem is that now u is not 0.
You will end up with a quadratic equation for t. Pick the positive solution.
 
  • #3
RUber said:
I am not familiar with SUVAT, could you provide more detail?
In your equation S = Ut+ .5At^2, the only thing that changes from your first problem is that now u is not 0.
You will end up with a quadratic equation for t. Pick the positive solution.

How would I isolate t?
 
  • #4
Rumplestiltskin said:
How would I isolate t?
Have you ever solved a quadratic equation?
 
  • #6
SteamKing said:
Have you ever solved a quadratic equation?

My bad, I was trying to rearrange for t. This crossroad is new to me.

120 = 2.5t + 4.9t^2
4.9t^2 + 2.5t - 120 = 0

A quadratic formula later... 4.7s. Correct! Thanks all.
 
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Related to Time to Fall 120m: Solving an SUVAT Problem with a Thrown Weight

1. How do I solve an Another SUVAT problem?

Solving an Another SUVAT problem requires using the equations of motion, which are S = ut + 1/2at^2, V = u + at, and V^2 = u^2 + 2as. You will need to have values for at least three of the variables (S, u, a, t, or V) and then use algebraic manipulation to solve for the unknown variable.

2. What are the units for the variables in Another SUVAT problems?

The units for the variables in Another SUVAT problems depend on the system of measurement being used. In the SI system, S is measured in meters (m), u and V are measured in meters per second (m/s), a is measured in meters per second squared (m/s^2), and t is measured in seconds (s).

3. Can I use Another SUVAT equations for any type of motion?

Yes, Another SUVAT equations can be used for any type of motion as long as the acceleration is constant. This includes motion in a straight line, motion with changing velocity, and motion with changing acceleration.

4. What is the difference between SUVAT and Another SUVAT equations?

The SUVAT equations are a set of four equations used to solve problems involving motion with constant acceleration. Another SUVAT equations are a set of three equations used to solve similar problems, but with a different set of variables.

5. Do I need to include air resistance in Another SUVAT problems?

No, Another SUVAT problems do not take into account air resistance. These equations assume that the object is moving through a vacuum and are only accurate for objects with constant acceleration.

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