## HW due 9/24

1)  Inertia is the tendency of an object to continue moving, or remain stopped, unless an outside force acts upon it to change it’s course of motion.

i) A personal experience I’ve had with the inertia of a moving object is when a pinecone fell out of a tree I was standing beneath and hit me on the head.  The force of my head caused the pinecone to slow from it’s constant falling speed, which ultimately was stopped by the supporting force of the Earth when it hit the ground.

ii) A personal experience I’ve had with the inertia of an immobile object was when Bo asked me to give him a push to help him start walking.  He asked me to help because he didn’t feel like he could move himself without the extra help from my muscles.  I pushed him and he began to walk.

2)  Yes, Newton’s First Law of Motion applies to large celestial objects such as the sun, the moon, and Earth.  Even though the giant objects are moving constantly because no outside force is acting upon them (inertia), at the same time, we are moving with them too and therefore cannot feel or see the movement.  We are moving at the same speed that the Earth is moving around the sun, yet we cannot tell because it’s all relative: this same notion applies to the Sun and the Moon.

3)  Net force is the collective amount of force (push or pull) exerted on an object by more than one force (gravitational, electrical, muscular, and magnetic).  The net force of an object is zero when two forces are pulling equally in opposite directions.  For example, if I’m holding a plate in my right hand, the force that gravity is exerting on the plate is equal to the force that my muscle is exerting on the plate to hold it up and steady.  This equal but opposite notion causes the net forces to sum to zero.  However, sometimes two opposite forces exerted on an object do not sum to zero.  For example, if the Hulk and Ken Lanik were playing tug o’ war, the forces that the Hulk and Ken Lanik are exerting on the rope are opposite, but Ken Lanik would clearly have the upper hand (therefore the forces are not equal).  Since Ken has the upper hand, the net force would be greater than zero because he is much stronger than the Hulk.

4)  The state of motion for an object that is experiencing zero net force is mechanical equilibrium.  Mechanical equilibrium is used to describe forces exerted on an object that are equal but that come from opposite directions.

5)  My seat is providing a support force in this instant because even though gravity is pushing my weight downward, the chair is holding my body upward.  The force it’s exerting against me to hold me up is equal to the force gravity is exerting to push me down.  My table is doing almost the same thing; it’s holding my computer up to support it, however, it’s working against both gravity and the force of my muscles typing away on the keyboard.