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Newton’s 1 st Law of Motion . Warm Up: 9/17. Please get the warm up from the front lab table. and turn it in to the cubby when complete. You can use your notes and Distance-Time/Speed-Time Graphs from last week.
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Warm Up: 9/17 • Please get the warm up from the front lab table. and turn it in to the cubby when complete. • You can use your notes and Distance-Time/Speed-Time Graphs from last week. • You will have approximately 7 minutes to complete this before we start today’s lesson.
Motion and Forces • All motion happens because there is a force. • Newton’s Laws describe the relationship between motion and force.
Forces • Forces are anything that make an object start moving or make an object slow down or stop. • There are balanced and unbalanced forces. • Unbalanced forces make an object start moving or they make an object speed up or slow down if it is already moving. • Balanced forces mean that an object is at rest or that it has a constant speed.
Newton’s 1st Law of Motion • If you slide your book across a carpeted floor, it will eventually stop. • Any ideas why? • What about if you slide a book across a surface like ice? • FRICTION!!!!
Newton’s 1st Law of Motion • Newton’s 1st Law of Motion states: “An object at rest will remain at rest and an object in motion will remain in motion unless acted on by an unbalanced force. • Why do you think there are seatbelts in cars? • http://teachertech.rice.edu/Participants/louviere/Newton/carandwall.gif
Newton’s 1st Law of Motion • Inertia is the tendency of an object at rest to remain at rest or an object in motion to continue in motion. • All objects resist changes in motion, so all objects have inertia. • Newton’s 1st Law is also called the “Law of Inertia”
Newton’s 1st Law of Motion • Mass is a measure of inertia. • An object with a small mass has less inertia than an object with a large mass. • Therefore, it is easier to move an object with a small mass. • Ex. It is easy to hit a baseball with a bat and send it flying in the air, but it is hard to do the same with a bowling ball.
Mass vs. Weight • All objects have mass. • Mass is the amount of matter an object has. • Weight is a measure of the gravitational force that is exerted on an object. • Remember that on Earth gravity is different than in space or on other planets (related to Earth’s size) • All objects feel a pull towards the center of the Earth which is why all objects fall downward at a rate of 9.8 m/s2 (constant rate that never changes!)
Mass vs. Weight • Even though your weight might be different, your mass will still be the same (what you are made of does not change!) • To calculate “true” weight, you must use the gravitational constant 9.8 m/s2 in the formula W=mg • W=weight (Newton, N) • M=Mass (Kilogram, kg) • G=Gravity (Same as acceleration, m/s2 )
Newton’s 1st Law Video Clip • http://www.youtube.com/watch?v=tbpqRSip4to • http://www.youtube.com/watch?v=7702nTbov9c&feature=related
Mass vs. Weight Practice • Note: 1kg. =2.2 lbs • To calculate your “true” weight, you would divide your weight in pounds by 2.2kg. • 150 lbs/2.2 kg/lbs=68.18 kg • Suppose you wanted to convert your weight from kg to pounds. You would simply multiply your weight by 2.2 kg. • 75kg x 2.2= 165 pounds