Forces
The Laws
Problems
100

What are contact forces?

Mechanical forces


Any force transmitted through physical contact.

100

What is Principia? 

His book on the his laws of motion, which describes the motion for most objects.

100

What is the weight of a 843.2 g cheez-it?

8.272 N

200

What is a force

Any interaction that can change the motion of an object

200
For the ancient Greeks, what is the difference between natural motion and unnatural motion?

Natural motion: An object wants to move towards a "preferred" position based off quality


Unnatural motion: All other motion.  Ex. flying arrow

200

If you kick a 14.3 kg chair with a force of 132.0 N, what would the acceleration of the chair be?  What is the force exerted by the chair on you? If you have a mass of 341 kg, what is your acceleration?

chair acceleration: 9.23 m/s2 forward


force on you: 132.0 N backward


your acceleration: .387 m/s2 backward

300

What is the strong nuclear force responsible for?

Chemical bonding


Binding forces together in the nucleus

300

Which law is expressed by Fa🠖b = -Fb🠖a?

Newton's third law

300
A piece of bridge is being held up from two pieces of string (on opposite sides of each other).  One is exerting a force of 63.2 N at 14o of the bridges vertical.  The other one is exerting a force of 17.2 N at 63o of the vertical.  What is the mass of the bridge?

7.156 kg

400

What is equilibrium?

The state at which the net force on a system is zero

400

Name and describe the four field forces that I gave you in this chapter.

Gravitational force - the attraction of one object on another object


Electromagnetic force - electricity and magnetism


Strong nuclear force - binds the protons and neutrons in the nucleus


Weak nuclear force - involved in nuclear fission and nuclear decay

400

A hunting bow imparts an acceleration of 4.30 * 103 m/s2 at an angle of 15.0o above the horizon to a 29.3 arrow.  What is the horizontal components of the force exerted by the bow on the arrow?

1.5 * 102 N forward

500

What is the mass of a 10 N person?

1.01 kg

500
Describe Newton's three laws of motion

1st Law - an object at rest stays at rest, an object in motion stays in constant motion unless acted upon by an external force

2nd Law - the acceleration of a system is directly proportional to the net force on a system, if both are heading in the same direction

3rd Law - to every action, there is an equal and opposite reaction

500

Lucas and Andi are pushing a 40.0 kg crate of Cheetos from the office to the end of the hallway.  Lucas is pushing at a 30o angle from the middle of the hall  with a force of 19 N.  Andi is pushing the crate with a force of 23 N at a 15o angle from middle of the hall.

a. What is the acceleration of the box?

b. What is the force exerted by the box on Andi as he is pushing it?

a. .971 m/s2 at 5.24o from the middle of the hallway.


b. -23 N at a 15o angle from the middle of the hall

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