- #1
Thoams Jerome
Rolls or brake falls slow down how fast your body hits the ground by well rolling.How does this decrease impacted.
If you roll when you hit the ground you feel less velocity?
Click For Summary
Discussion Overview
The discussion revolves around the mechanics of rolling or braking falls and their effects on the impact experienced when hitting the ground. Participants explore the physics behind deceleration, momentum change, and the implications of different falling scenarios, including the use of objects in free fall.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- Some participants suggest that rolling or braking falls reduce the peak acceleration experienced upon impact by extending the duration of deceleration.
- Others emphasize that the key factor is not just rolling, but the overall time over which deceleration occurs, which can lower the average force experienced.
- One participant references the saying, "It's not the fall that kills you, it's the sudden stop at the end," to highlight the importance of reducing the suddenness of the stop.
- Several participants inquire about the equations related to impulse and momentum change, with one providing the formula F = ΔP/Δt to illustrate the relationship between force, momentum, and time.
- There are questions regarding specific scenarios, such as whether a board wedged inside a trash can will jump up when the can hits the ground, and the physics involved in such situations.
- One participant expresses confusion about the connection between rolling and the inability to compress oneself, prompting further clarification about the mechanics of bending and rolling upon impact.
Areas of Agreement / Disagreement
Participants present multiple competing views on the mechanics of rolling and its effects on impact, with no consensus reached on the specific scenarios discussed or the implications of the physics involved.
Contextual Notes
Some discussions involve assumptions about the behavior of objects in free fall and the effects of friction, which may not be fully resolved. The mathematical explanations provided rely on calculus concepts that may not be universally understood among participants.
- #2
mfb
Mentor
- 37,451
- 14,318
It is not so much the rolling itself, it is making the deceleration last longer, which means you get a lower peak acceleration. As you can't compress yourself to a point, you have to go sidewards.
- #3
- 3,766
- 1,981
As an old saying goes: "It's not the fall that kills you, it's the sudden stop at the end." Rolling lessens the "suddenness" of the stop.
- #4
Thoams Jerome
Does anyone have the equation for that?
- #5
Thoams Jerome
How does not being able to comprising yourself to a point, effect you going sidewards?Also if you dropped a object like a box with lightly connected object to hollow space.Like putting a rock that's lighter then the box in the top connected with toilet paper.then dropping it down would the rock go up and take some the energy from the fall with it?mfb said:
- #6
Drakkith
Mentor
- 23,205
- 7,687
Thoams Jerome said:
I'm sorry but I can't make any sense out of this.
- #7
berkeman
Admin
- 69,539
- 25,123
I think he's asking about jumping up in a falling elevator to lessen the impact at the bottom (maybe), but I'm not getting the toilet paper angle...Drakkith said:
- #8
Thoams Jerome
Sorry.If you drop a trash can with a light board lightly wedged inside.Will the board jump up when the trash can hits the ground?What are the physics involved.berkeman said:I think he's asking about jumping up in a falling elevator to lessen the impact at the bottom (maybe), but I'm not getting the toilet paper angle...
- #9
pixel
- 545
- 147
Thoams Jerome said:
In a fall, you are changing momentum from some initial value to a zero final value. The change in momentum equals the Impulse, which is the integral of the force (in this case the force causing the deceleration) over time. If you can increase the time over which the force acts, less force on average is required. If you don't use a brake or roll fall, the time interval is much smaller so the force is larger to produce the same momentum change.
If you don't know calculus, instead of the integral of force over time just think in terms of the product of the average force and the time interval over which the force acts.
- #10
Drakkith
Mentor
- 23,205
- 7,687
Thoams Jerome said:
The board will likely become un-wedged and fall to the bottom of the trashcan upon impact. During the impact, the board experiences a large force from friction that attempts to decelerate it. If, before the board decelerates, it slides enough to break loose completely then it will fall to the bottom.
- #11
mfb
Mentor
- 37,451
- 14,318
It doesn't, and no one said that.Thoams Jerome said:
It is advisable to go sidewards. Bending your knees is an example already, and starting to roll is an extension of that approach.
- #12
Kaura
- 122
- 22
Thoams Jerome said:
F = ΔP/Δt
Force known in this case as Impulse is equal to a body's change in momentum divided by the change in time. Momentum is the object's mass multiplied by its velocity. From this equation you can see that the longer it takes for the momentum to reach zero the less force acts on a body. In the example of rolling when hitting the ground, doing such a thing gives the person's body more time to change its momentum to reach rest. It is also why landing on a cushion from a high height is far less likely to hurt you compared to landing on concrete. The cushion allows for your body to slow down over a longer period of time.
Similar threads
- · Replies 2 ·
- · Replies 4 ·
- · Replies 4 ·
- · Replies 10 ·
- · Replies 12 ·
- · Replies 5 ·
- · Replies 4 ·
- · Replies 7 ·
- · Replies 24 ·