Warmup Sept 17 th - Think. You were kidnapped and knocked out. Some time later, you wake up in a dark warehouse. All there is in the room is a scale and a light, so you decide to weigh yourself. WOW!!! You gained a whole lot of weight last night…what happened?
Fg = mg (formula for weight)
is the force an object has due to gravity Gravity on the Earth 9.8m/s2
What’s the mass of my 893N ex-husband that just happens to be in my basement?
Force equals mass times acceleration.
if M then A
My 4 kg cat, Jeter, ran at our kitten Shadow with an acceleration of 3.0 m/s2. He didn’t stop. Poor little kitten! After suffering a mild concussion, we wondered….how much force did Jeter hit him with?
Force = mass x acceleration, or…
4 x 3 = 12
Remember Force has its own special unit…
1kg x 1m/s2 = 1 newton (1N)
F = ma
Learn it. Live it. Love it.
1. How much force is needed to push a lawnmower of 30 kg at 2.5 m/s2?
2. How much force must be applied to a bowling ball that has a mass of 5kg to achieve an acceleration of 25m/s2?
3. What is the mass of a baseball that has an acceleration of 125 m/s2 after a force of 44 Newtons has hit it?
4. What is the acceleration of a 22kg wolf that hits attacks a bear with a force of 400 Newtons?
Friction - a force that opposes motion, or “pushes back” when two surfaces are touching.
It’s always around and it affects everything.
1) Static friction: Friction that resists the start of sliding motion between two objects at rest.
Keeps things stopped
2) Kinetic friction: The force that opposes the movement of two surfaces that are in contact and moving over each other.To make something move, you just overcome static friction by pulling with a force larger than kinetic friction.
Sliding or Rolling
3) Fluid friction: The friction between layers of a fluid.
2 types- Liquid and Gas
Liquid- water, oil etc.
Gas - Air
Described by viscosity.
Viscosity – the “thickness” of a fluid.
Low viscosity = “thin;”
High viscosity = “thick” or “viscous.”
The less viscous a fluid is, the easier it moves.
I’m talking about Mass or surface area folks!