1. Newton’s 1 st Law of Motion, Weight & Applying Newton’s 2 nd Law Chapter 6.2 System

2. What You Already Learned Newton’s 2 nd Law of Motion.

3. Inertia was a term first coined by. –He suggested that objects in motion would remain so unless acted upon by. –Inertia is an objects to in. For two objects of the same size, the more an object has, the more it has.

4. Newton’s 1 st Law of Motion Newton later revised Galileo’s theory: –An object in motion will remain in motion in a with unless acted upon by an force. and –An object at will remain at unless acted upon by an force. Newton’s 1 st Law of motion is also known as the.

5. Inertia and Motion If the net sum of external forces on an object was equal to zero, would the object change direction or accelerate? –If the forces are, then or change in will occur. F forward F friction F ground-on-car F gravity If the forces are, then the vehicle will continue to travel at a. System

6. Misconceptions about Forces Is a force required after a ball is released while throwing to make it continue in its path? : once the contact force between the hand and the ball are broken, there is a force propelling the ball forward.

7. Misconceptions about Forces Is inertia a force? – : Inertia is the tendency for an object to a change in. –Inertia is a property of. –The more an object has, the more it has. –Forces that exist in the environment on objects.

8. Misconceptions about Forces Does air exert a force? – Objects that are not moving relative to their surroundings experience a of due to the air in the atmosphere (Barometric pressure = 101.3 Pa = 14.7 psi). Objects in motion experience, a due to air acting on the side of the object facing the direction that it is moving. As the - increases the increases. –Ex. Air drag on skydivers, automobiles, etc.

9. What’s the difference between mass and weight? is a property of an object that (provides a numerical value) for the amount of ( and ) that it contains. is a measure of the exerted on a body by, which is directly related to the amount of and due to gravity. is the same everywhere in the, while will vary with the mass and distance from other bodies. NOTE: AND ARE THE SAME!

10. Determining Weight If the mass of an object is known, its weight can be determined using Newton’s Law of Motion. oF g = Where: m = g = to (g = ).

11. Example: Mass vs. Weight On Earth: –Mass = __ kg –Weight = ___ N On the Moon: –Mass = __ kg –Weight = _____ N (g m = 1.62 m/s 2 ) Why is the weight on the moon so much less? –Because the gravitational force of attraction on the moon is _____ that on Earth. Note: The is the same on both the Earth and the Moon.

12. Example 1: How will your weight change? You have a mass of 75 kg and are standing on a bathroom scale in an elevator. The elevator accelerates from rest at a rate of 2.0 m/s 2 for 2 s and then continues at constant speed. 1.What is the scale reading during acceleration? 2.How does this reading compare to that of the scale at rest? 3.How does this reading compare to that of the scale when the elevator is moving at constant v?

13. Diagram Problem System +y F net =

14. State the Known and Unknowns What is known? oMass (m) = ___ kg oAcceleration (a) = ___ m/s 2 oTime (t) = ___ s What is not known? oF scale = ?

15. Perform Calculations F net = Where: oF net = oF gravity = oF scale =

16. Scale Reading at Rest and Constant Speed When the elevator is at rest or not accelerating, equation (1) [ F net = ] reduces to: Since the forces are, there is (Newton’s 1 st Law of Motion) and F Net =.

17. Key Ideas Inertia is a measure of an objects to change in motion. Newton’s 1 st Law of motion is also known as the. Size being equal, the more a body contains, the more it has. If the sum of the forces on a body equal, then the object will remain at, or remain in motion at a.

18. Key Ideas is a property of a material that is a measure of the amount of it contains. is a measure of the force on an object that is proportional to its and due to.