7 th Grade Science Unit 5 NCFE Review

Transcription

1 7 th Grade Science Unit 5 NCFE Review

2 Motion Mo#on: defined as a change in the posi#on of an object results in movement judged rela#ve to a reference point

3 Speed the distance an object covers over #me can be calculated using the formula: speed = distance,me

4 Reference Point Reference point: defined as an object or loca#on that is used to determine if another object is in mo#on. are most o/en sta#onary (not moving).

5 Measuring Distance When we describe motion, we use units to talk about the distance an object moves. The formula to find distance is Speed X Time. When we measure distance, you are measuring the change in location. Units: length (meters, yards, miles, etc.)

6 Acceleration Acceleration is a CHANGE in motion An object is accelerating if it is: l Speeding up l Slowing down l Changing direction

7 Calculating Acceleration Acceleration is the change in speed per unit of time. Final speed Initial Acceleration = Speed Time Acceleration is measured in units of meters per second per second, or m/s 2.

8 Graphing Motion Steady Motion NO motion

9 FAST vs. SLOW FAST SLOW

10 Other Motion Graphs Starting and Stopping. Accelerating/Speeding Up

11 FORCES A FORCE is a PUSH or PULL in a particular DIRECTION. When 2 or more forces act on an object, the forces combine to form a net force. Forces may work together -> Or oppose each other -> <-

12 FORCES If the forces cancel each other out, and do not cause the object to move, the forces are said to be BALANCED. If the forces don t cancel each other out 1 force is stronger than the others the forces are UNBALANCED and will cause a CHANGE IN MOTION.

13 COMBINING FORCES Two forces in the same direction can add together to produce a larger net force. + = 5 N right 5 N right 10 N right

14 COMBINING FORCES Two forces in opposite directions can subtract to produce a smaller net force in the direction of the larger force. - = 5 N right 10 N left 5 N left

15 - What is Friction? Friction is a force that two surfaces exert on each other when they rub against each other. The direction of the friction force is always OPPOSITE to the direction of the motion. It SLOWS down moving objects! Direction of Motion Friction Force

16 The Force of Gravity Gravity is the force that pulls all objects down to the earth. Air Resistance helps slow down things that are being pulled by gravity and falling. (It is a form of friction.)

17 What is WORK? In scientific terms, you do WORK when you exert a FORCE that causes an object to move some DISTANCE in the SAME DIRECTION of the force. WORK = FORCE x DISTANCE

18 If the motion is in a different direction than the force, there is no work. What 2 things must happen for WORK to be done? MOTION The object must move. If the object doesn t move, there is no work done. FORCE & MOTION IN THE SAME DIRECTION Movement must be in the same direction as force.

19 What is POWER? Power is the rate at which work is being done (or how much work is being done in a unit of time). POWER = WORK TIME More power means less time to do the same work OR more work done in the same amount of time. Power is measured in Watts (W).

20 Energy is: the ability to do WORK or cause change There are two main kinds of energy POTENTIAL ENERGY KINETIC ENERGY STORED energy or Energy that is NOT being used Energy that IS being used or Energy in MOTION Examples: Examples:

21 There are 6 forms of energy: mechanical, chemical, nuclear, electromagnetic, thermal, electrical. Energy can change from one form into another but is not created or destroyed. Review: There are two TYPES of energy: potential and kinetic. Energy can t be created or destroyed so we need to convert energy we have into what we need. The energy we use comes from many sources: Fossil fuel (coal, oil, natural gas), nuclear power, sun, wind, geothermal, hydropower. Most of this we convert into electricity (electrical energy).

22 What are MACHINES? Most people think of complex, automated, technical, or electronic gadgets with motors, but machines can be much simpler. A machine is any device that lets you do WORK in an easier or more effec+ve way.

23 How do Machines do work? Machines make work easier by changing 3 things about the FORCE you exert to do work: v AMOUNT of force you exert v DISTANCE over which you exert force v DIRECTION in which you exert force

24 What are SIMPLE MACHINES? There are only 6 basic kinds of simple machines that make work easier. These 6 simple machines make up all the other compound machines we use everyday.

25 SIX SIMPLE MACHINES The six simple machines are: Inclined Plane Wedge Screw Lever Wheel & Axle Pulley

26 What is this electrical poten#al called? Sta#c Electricity

27 Electricity that moves..(kine#c electricity) Current: The flow of electrons from one place to another. Measured in amperes (amps) How can we control currents? With circuits. Circuit: is a path for the flow of electrons. We use wires.

28 There are 2 types of currents: Direct Current (DC) Where electrons flow in the same direc#on in a wire. Alterna,ng Current (AC) electrons flow in different direc#ons in a wire

29 2 types of Circuits: 1) Series Circuit Series Circuit: the components are lined up along one path. If the circuit is broken, all components turn off.

30 There are 2 types of circuits: 2) Parallel Circuit Parallel Circuit there are several branching paths to the components. If the circuit is broken at any one branch, only the components on that branch will turn off.

31 2 types of Circuits: 2) Parallel Circuit

32 Conductors vs. Insulators Conductors material through which electric current flows easily. Insulators materials through which electric current cannot move.

33 What is magnetism? Magnetism is the properties and interactions of magnets The earliest magnets were found naturally in the mineral magnetite which is abundant the rock-type lodestone. These magnets were used by the ancient peoples as compasses to guide sailing vessels. Magnets produce magnetic forces and have magnetic field lines

34 Magnets have two ends or poles, called north and south poles. At the poles of a magnet, the magnetic field lines are closer together. Unlike poles of magnets attract each other and like poles of magnets repel.

35 The earth is like a giant magnet! The nickel iron core of the earth gives the earth a magnetic field much like a bar magnet.

36 What is an electromagnet? When an electric current is passed through a coil of wire wrapped around a metal core, a very strong magnetic field is produced. This is called an electromagnet.