Impulse

How hard is it to stop a moving object? Bringing an object to a stop requires a force applied over some period of time. This is called impulse. I = FΔt

CHANGING MOMENTUM Ft Decreasing Momentum Which would it be more safe to hit in a car ? Knowing the physics helps us understand why hitting a soft object is better than hitting a hard one. Ft mv mv Ft

Spreading impulse out over a longer time means that the force will be less; either way, the change in momentum of the boxing glove, fist, and arm will be the same.

DECREASING MOMENTUM EXAMPLES : Padded dashboards on cars Airbags in cars or safety nets in circuses Moving your hand backward as you catch a fast-moving ball with your bare hand or a boxer moving with a punch. Flexing your knees when jumping from a higher place to the ground. or elastic cords for bungee jumping Using wrestling mats instead of hardwood floors. Dropping a glass dish onto a carpet instead of a sidewalk.

Linear momentum & impulse Examples of impulses being applied on everyday objects

IMPULSE = CHANGING MOMENTUM In each case, the momentum is decreased by the same amount or impulse (force x time) Hitting the haystack extends the impact time (the time in which the momentum is brought to zero). The longer impact time reduces the force of impact and spreads out the deceleration rather than instantly. Whenever it is desired to DECREASE the FORCE of impact, EXTEND the TIME of impact !

What does this gymnast do to lessen the impact of landing? She bends her knees, spreading the force out over a longer amount of time

Why does an egg break when dropped? An egg dropped on a tile floor breaks, but an egg dropped on a pillow does not. Why? FΔt= mΔv In both cases, m and Δv are the same. If Δt goes up, what happens to F, the force? Right! Force goes down. When dropped on a pillow, the egg starts to slow down as soon as it touches it. A pillow increases the time the egg takes to stop.

Now that you understand! Check out some of the videos and think about Impulse / Momentum Think about energy transfer Super slow motion FACE SLAP 1959 Chevy Bel-Air vs. 2009 Chevy Malibu Amazing billiards in slow motion Time warp water balloon to the face