Gravity the attractive force between two objects Gravity

*Gravity - the attractive force between two objects. *Gravity is between everything (if you’re holding an apple, there’s a gravitational force between you and the apple), but 99. 9% of the time we only care about it when it’s between us and the planet we’re standing on (so us and Earth). *

*Mass – how much space an object takes up, or how much matter is in something. *Mass doesn’t change based on location. You will have the same mass on earth as you would on the moon, on Mars, or on Jupiter.

*Weight – how strong gravity’s pull on something’s mass is. *Weight DOES change based what planet the object is on. Gravity’s pull, for example, is stronger on earth than on the moon, so someone would weigh less on the moon than they would on earth.

*Weight = Gravity x mass. *W=g*m. *That is the formula we use to calculate weight problems.

*Momentum is a measurement of inertia. It measures the inertia that is acting upon an object at any given time. *To calculate this measurement of inertia, we need how fast the object is moving (it’s velocity), and the mass of the object. *

*Momentum = mass x velocity *p=m*v *We use “P” for momentum because “m” was already used for mass, and that would be confusing for scientists to use two m’s in a simple equation like this.

*When two objects collide, the net momentum stays the same, though it may be distributed differently. *That’s how this toy works: when one ball hits another, it may stop, but the momentum moved onto the ball that had been standing still. *

*Torque – a force applied with leverage. *Torque changes an objects rotational motion. *

*Torque = (perpendicular) Force x Distance (level arm) *Or T = F*d *Distance = point from where you’re applying force to the pivot point, where your lever is rotating.

*Torque is a vector, because the direction the force is applied matters. *To be fully effective, the force must be perpendicular to the lever.

*Because we are facing the objects, we call the direction of the applied rotational torque “clockwise” or “Counter clockwise. ”

*When calculating the total torque of a longer, confusing problem, we add the torques for all clockwise motion and all counter clockwise motions, and subtract the smaller number from the larger. That gives us the net torque in one direction.