Transcript Motion and Machines - Effingham County Schools

S4P3
• Position is an object’s location or place.
* Ex: where you desk is located in the classroom
• Motion is a change in an object’s position as
compared to objects around it.
*If you move your desk, its position changes. It’s position changed as
compared to the walls.
An object’s location is its (position/motion).
The change in an object’s place as compared to
objects around it is called (position/motion).
How can passengers in a car tell that they are moving?
Speed is a measure of the distance an object
travels in a certain amount of time.
Speed is measured using units of distance and
time.
You need to know the distance an object has
traveled and how long it took to travel that
distance find the speed of an object.
divide distance by time to find speed
* ex: A car traveling 100 miles in 2 hours. Divide
the distance (100 miles) by the time (2 hours)
100 ÷ 2 = 50 miles per hour (mph)
Look at the chart of race results.
2-mile race results
Runner 1
15 min 32 s
Runner 2
18 min 50 s
Runner 3
20 min 45 s
Which runner has the slowest
speed?
Which runner has the fastest
speed?
How do you know?
The measure of the distance an object travels in a
certain amount of time is called:
a. position
b. motion
c. speed
d. frame of reference
List the two measurements you need to know in
order to calculate speed,
Direction tells you which way an object is
moving
ex: east, west, north, south, right, left, up, down,
etc.
Velocity is a measure of speed in a certain
direction.
Speed and direction together determine, or
set, velocity.
direction
velocity
All the cars are
traveling 70m/hr.
The cars are
constantly
changing
direction. What
else is changing?
Forces are pushes or pulls that cause objects to
change their motion. Friction and gravity are to
important natural forces.
The man pulls on the
rake and the leaves
move toward him.
The boy pushes the
wheelbarrow and it
moves away from
him.
A force can change the motion of an object and
a force can stop an object from moving.
Which box would take more force to move
across the floor?
1 kg
10 kg
When you stop pushing a heavy box, a different
force stops the box from sliding. That force is
called friction.
Friction is a force that slows or stops motion
between two surfaces that touch each other.
Rough surfaces have more friction than smooth
surfaces
Friction between the
brake and the wheel on a
wheel chair stops the
wheel from turning when
the brake is used.
Friction keeps things from slipping and sliding.
ex: holding a pencil
There is even friction between objects and the
air.
ex: air resistance between air and a bicycle
Friction slows or stops movement.
Sometimes, less friction is better. For example, less
friction between snow and a snowboard lets the
snowboarder go faster.
Add a slippery
matter on
surfaces that
touch
Wheels allow
objects to roll
over a surface
How can a force change the motion of an
object?
Which objects would produce the least amount
of friction when rubbed together?
Two sheets of sandpaper
two ice cubes
How does friction stop a bike?
sandpaper and an ice cube
Reducing friction might be useful in which of
the following activities?
walking
ice skating
using a pencil
stopping a bike snowboarding skiing
What are some ways to reduce friction?
Gravity is a force that pulls objects towards each
other.
Gravity pulls skydivers toward the Earth
The force that holds the moon in orbit around
the Earth is called
a. Friction
b. gravity
c. motion
d. velocity
Forces are pushes or pulls that cause objects to
change their motion. Friction and gravity are
two important natural forces. Look at the
bowling ball below. What force is acting at each
arrow?
Simple machines help people do work by
changing a force.
A simple machine is a tool that makes work
easier by changing a force.
A simple machine allows you use less force to
move an object.
An inclined plane is a simple machine that is
made up of a slanted surface
It helps increase the distance over which force is
used.
It makes work easier
A wedge is a simple machine made up of two
inclined planes.
Shaped like the letter V.
It changes downward force to and outward
force.
This helps cut or split objects apart.
A screw is a simple machine made up of an
inclined plane wrapped around a post.
It changes the direction of a force from a
turning force to a downward force.
The threads of a screw are in inclined
plane. The turning force of a screw easily
pushes into wood.
A lever is a simple machine made up of a stiff
bar that moves freely on a fixed point called a
fulcrum.
A small force is used on the long end of a lever
which creates a large force at the short end.
A wheel and axle is a simple machine made up
of two cylinders that turn on the same axis.
Using a wheel and axle makes work easier.
A water faucet is a wheel and axle. You use a
small force to turn the wheel. This creates a
large force that turns the axle.
A pulley is a simple machine made up of a rope
fitted around the rim of a fixed wheel.
Pulleys increase the force or change the
direction of the force
You pull down on one
end of a rope on a
pulley to raise a flag or
other object.
Describe a pulley.
How does the rope and pulley on a flagpole
change the direction of the force?
Think about a sport or other activity that you
enjoy. Describe the forces – pushes, pulls,
gravity, and friction – that you use during the
activity.