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Forces Change Motion 2.1 Phoenix Science 2010. Force A push or a pull.

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Presentation on theme: "Forces Change Motion 2.1 Phoenix Science 2010. Force A push or a pull."— Presentation transcript:

1 Forces Change Motion 2.1 Phoenix Science 2010

2 Force A push or a pull

3 Types of Forces Contact Forces - friction Non-Contact Forces - gravity - magnetic

4 Contact Force When one object pushes or pulls another object by touching it.

5 Gravity the universal force of attraction between two masses. (non-contact)

6 Friction a force that resists motion between two surfaces that are pressed together. (contact)

7 Net Force All of the forces acting upon an object combined. Balanced forces cannot change an object’s motion. Unbalanced forces are needed to change an object’s motion.

8 Newton’s First Law INERTIA –Objects at rest, stay at rest, and objects in motion, stay in motion, with the same velocity unless acted upon by an unbalanced force.

9 Inertia Resistance of an object to change in its motion.

10 Force and Mass determine acceleration 2.2 Phoenix Science 2009

11 Newton’s 2 nd Law Acceleration of an object increases with increased force and decreases with increased mass. What 3 concepts are involved here?

12

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14 Force = m x a Force = mass x acceleration F = ma Force is measured in Newtons –ex. Force = 40 N

15 Math to blow your mind Acceleration = Force / mass Mass = Force / acceleration I’ve got to show you this on the board. Don’t worry if you don’t get it the first time.

16 2.3 Forces act in pairs Phoenix Science 2008

17 Newton’s 3 rd Law Every time an object exerts a force on another object, the second object exerts a force that is equal in size and opposite in direction back on the first object. Action – Reaction Pairs.

18 Newton’s 3 Laws describe and predict motion. Reread p. 61

19 2.4 Forces transfer momentum Phoenix Science 2008

20 Momentum a measure of mass in motion p=mv measured in kg * m/s

21 Collision a situation in which two objects in close contact exchange energy and momentum. read about the two types on p. 68.

22 conservation of momentum the total momentum of a system of objects does not change, as long as no outside forces are acting on that system. Another way of looking at Newton’s 3 rd Law.

23 air resistance friction due to air molecules, also referred to as drag.

24 Solve for force: m = 75 kg, a = 3 m/s²

25 Solve for force: m = 4 kg, a = 6 m/s²

26 Solve for acceleration: F = 45 N, m = 15 kg

27 Solve for force: m = 5 kg, a = 8 m/s²

28 Solve for mass: F = 75 N, a = 5 m/s²

29 Solve for acceleration: m = 15 kg, F = 60 N

30 Solve for mass: F = 12 N, a = 6 m/s²

31 Solve for mass: F = 220 N, a = 11 m/s²

32 Solve for force: m = 70 kg, a = 5 m/s²

33 Solve for Momentum: m = 1.5 kg v= 2 m/s

34 Solve for Momentum: m = 20 kgv= 30 m/s

35 Solve for Momentum: m = 0.5 kgv= 0.25 m/s

36 Solve for Momentum: m = 15 kgv= 1.5 m/s


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