Question

lesson 6: force and work
newton’s laws of motion
-one of the millions of scientists who changed the world!
-______ laws developed by newton to explain why things moved (or didn’t move)
first law of motion
-“a body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force.”
-objects do not start, stop, or change direction all by themselves, they need a force acting on them.

• inertia - property of objects to resist changes to their motion

second law of motion
-“the force acting on an object is equal to the mass of that object times its acceleration.”
-when force is ____ to an object at rest, it accelerates in the ________ of that force

• f = ma, where f is force, m is mass, and a is acceleration

third law of motion
-“for every action, there is an equal and opposite reaction.”
-forces occur in pairs: when one object pushes against another, the second object pushes back just as hard
si units
-all ____ measurements should be done in ____ not pounds

• to convert: m(kg)=m(lb)×0.454

force
-a push or pull that causes an object to either move faster, ______, or in a different direction
-2 kinds of forces:

• __________: two objects directly interact with each other
• friction: occurs when two objects rub
• pulling: pull or push an object
• ____________________ forces: occur without direct contact
• gravitational pull of the sun on earth

calculating force
-force has the following formula: f = ma (force = mass x acceleration)
-f = force measured in newtons (n)
-m = mass in kg
-a = acceleration in meters per second squared (m/s²)
ex 1. find the force that is required to accelerate a 1,500 kg car at 5 m/s².
calculate the force required for an 8 - pound wagon to accelerate at 7 m/s² (hint: convert the pounds to kg first).

Explanation:

Step1: Convert pounds to kg

Given the conversion formula $m_{(kg)}=m_{(lb)}\times0.454$, for an 8 - pound wagon, $m = 8\times0.454=3.632$ kg.

Step2: Calculate the force

Using the formula $F = ma$, where $m = 3.632$ kg and $a = 7$ m/s². So $F=3.632\times7 = 25.424$ N.

Answer:

25.424 N