Resume of Science
Momentum and Impulse
Momentum: Is a property of moving objects. It is inertia in motion, or more specifically
the mass of an object multiplied by its velocity. If the momentum of an object changes,
then either the mass or the velocity or both change.
Formula: m x v
Impulse: Change in momentum. The greater the impulse exerted on something, the
greater the change in momentum.
Formula: f x t
Cases in which momentum increase or decrease
CASE 1: INCREASING MOMENTUM
Sense to apply the greatest force possible for as long as possible.
CASE 2: DECREASING MOMENTUM OVER A LONG TIME
When the time of hit is longer the impact force is lower.
CASE 3: DECREASING MOMENTUM OVER A SHORT TIME
When the time of impact is shortest the impact force is higher.
Relationship between collisions
Elastic collision- the colliding objects rebound without lasting deformation or the
generation of heat
Inelastic collision- characterized by deformation, generation of heat, or both
Formula:
Law of Conservation of Momentum
Law of conservation of momentum: “In the absence of an external force, the momentum
of a system remains unchanged”
SI Units
Speed/velocity
Initial Velocity
Final Velocity
Time
Momentum
Distance
Impulse
Force
Mass
Work
Power
m/s
Vi
Vf
s
Kg.m/s
m
N.s
N
kg
Joules
Watts
Work
Is the transfer of energy to an object by using a force that causes the object to move in
the direction of the force. For work to be done on an object, the object must move in the
same direction as the force.
If there is no change in the object`s energy, no work was done on it.
Formula: f . d
Difference between Force and Work, Kinetic Energy and Work
Applying a force doesn’t always result in work being done.
When an object is moving, then it is capable of doing work. It has energy in motion.
Kinetic and Potential Energy
KE: m. v. v
2
PE: m. g. h
Power
Power is the rate at which energy is transferred.
Formula: W/t
Simple and Compound Machines
A machine is a device for multiplying forces or simply changing the direction of forces.
Compound machines are machines that are made of two or more simple machines.
Different types of machines
Lever
A lever is a simple machine that has a bar that pivots at a fixed point, called a fulcrum.
First-Class Levers With a first-class lever, the fulcrum is between the input force and the
load.
Second-Class Levers The load of a second-class lever is between the fulcrum and the input
force.
Third-Class Levers The input force in a third-class lever is between the fulcrum and the
load.
Inclined Planes
An inclined plane is a simple machine that is a straight, slanted surface.
Pulleys
A pulley is a simple machine that consists of a wheel over which a rope, chain, or wire
passes.
Fixed Pulleys A fixed pulley is attached to something that does not move.
Movable Pulleys Unlike fixed pulleys, movable pulleys are attached to the object being
moved.
Blocks and Tackles When a fixed pulley and a movable pulley are used together.
Wheel and Axle
A wheel and axle is a simple machine consisting of two circular objects of different sizes.