Download presentation

Presentation is loading. Please wait.

Published byGregory Bailey Modified over 7 years ago

1
Chapter 4 Physics

2
Section 4-1 I. Forces A. Def- a push or pull; the cause of acceleration. B. Unit: Newton Def- amt. of force when acting on a 1 kg mass produces an acceleration of 1 m/s 2 1N = 1 kg m/s 2

3
Cont: C. Conversions 1 lb = 4.448 N 1N = 0.225 lb D. Kinds of forces 1. Contact force- physical contact 2. Field- exists, even in absence of contact ex. Gravity, electricity Especially important in nuclear & particle physics

4
II. Force Diagrams A. Force is a vector. B. Def- a diagram of the objects involved in a situation and the forces exerted on the objects.

5
III. Free – body diagram A. Shows forces on 1 object. B. Does not show forces exerted by the object. C. Drawing a free-body diagram. 1. Simple diagram visualizing the object. 2. Draw and label vector arrows representing all external forces.

6
Section 4-2 Newton’s 1 st Law I. Inertia- 1 st realized by Galileo in 1630’s A. An object at rest will stay at rest in the absence of external forces. -An object in motion will stay in motion….. B.Further developed by Newton in 1687 1 st law C. When net external force on an object is zero, its acceleration is zero.

7
Cont: II. Forces A. External force- single force acting on the object. B. Net External Force- vector sum of all the forces acting on a body. (resultant force) C. Sample problem 4A 1. Make a free body diagram 2. Find x & y components of all forces. 3. Find net external forces 4. Evaluate your answer.

8
III. Inertia A. Def- the reluctance of any body to change its state of motion. B. Mass is a measurement of inertia. *1. Mass is not weight. a. Mass- amt of matter in a body b. Weight- pull of gravity on an object. 1 Kg. = 9.8 Newtons W = mg

9
IV. Equilibrium A. An object is in =ibrium when all net forces = 0. Ef y = 0 Ef x = 0 B. At rest or moving w/ constant velocity.

10
Section 4-3 I. Newton’s 2 nd Law- the accel. of an object is directly proportional to net external force acting on the object, and inversely proportional to its mass.F= ma

11
II. Newton’s 3 rd Law A. Forces always exist in pairs. B. The force exerted on object A by B is equal and opposite to the force on B by A. C. One force is the action the other force is the reaction. D. The forces do not balance each other- they act on different objects.

12
Section 4-4 I. Everyday Forces A. Weight- the pull of gravity on an object. 1. Weight will change; mass will not change w= mg B. Normal Force- a contact force acting to the surface of contact. 1. Opposes gravity, but not necessarily parallel to gravity.P. 142 fig 4-20 2. to surface.

13
C. Friction Forces 1. Static Friction- force exerted on a motionless body by its environment to resist an external force. 2. Kinetic Friction- the force exerted on a moving object. a. than static friction. 3. Depends on the 2 surfaces.

14
II. Coefficient of Friction Coefficient of Friction- ratio between static friction and the normal force. s = F s max/ F n k = F k / F n

15
III. Air Resistance = F r A. To car’s speed When F r = speed, accel = 0.

Similar presentations

© 2023 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google