Study Guide Chapter 11

Forces

1. What is a force? (pages 374 – 377)

A. Define forces and give examples.

B. A Newton (N) is the unit for measuring a force like weight.

C. Net Force – the combination of all forces acting on an object. When two or more forces act in the same direction, add the forces. When two or more forces act in opposite directions, add them together but one of the forces is acting in a “negative” direction so it’s like adding positive and negative numbers.

D. Unbalanced Forces – When there is a net force acting on an object. Basically there is more push or pull from one direction than the other. This means that there will be a change in the object’s velocity in the direction of the greatest force.

E. Balanced Forces – Equal forces acting on one object in opposite directions. Balanced Forces do not change an object’s velocity.

2. Friction, Gravity (pages 380 – 388)

A. Friction – A force that two surfaces exert on each other when they rub up against each other. It acts in a direction opposite to the motion of objects.

B. Without friction or another unbalanced force, a moving object will not stop until it strikes another object.

C. Friction is caused by the irregular and bumpy surfaces of objects. The bumpier the surface, the more friction. Friction also depends on how hard the surfaces push together.

D. Types of friction:

1. Static Friction – Right before an object starts to move.

2. Sliding Friction – Two solid surfaces slide over one another.

3. Rolling Friction – When an object rolls over a surface.

4. Fluid Friction – When a solid object moves through a fluid like water or air. Air resistance is a type of fluid friction.

E. Gravity – Force that pulls objects together. Gravity is caused by mass. The more mass an object has, the greater the gravity. The closer objects are to each other, the more gravity will affect the objects.

F. Weight = mass x acceleration due to gravity (9.8 m/s )

G. Free Fall – When the only force acting on as object is gravity. All objects in free fall accelerate at the same rate regardless of mass. Air resistance can slow objects down if their shape is changed to increase air friction. Terminal Velocity is when the downward force of gravity and the upward force of drag are equal on a falling object.

H. Projectile Motion – If an object is given horizontal motion as well as vertical, the motions are independent of each other. Throwing an object harder in a horizontal direction will not make it drop slower. It will travel farther per second away from the drop point than an object thrown will less force but it will fall toward Earth at the same rate.

3. Newton’s Laws of Motion (pages 389 – 397)

A. First Law of Motion – Objects at rest tend to stay at rest unless acted upon by an outside force. Objects in motion tend to stay in motion unless acted upon by an outside force.

1. Inertia – Tendency of an object to resist a change in motion.

B. Second Law of Motion – Force = Mass x Acceleration

C. Third Law of Motion – For every action there is an equal but opposite reaction.

D. Momentum – Quantity of motion that depends on the mass of an object and its velocity. People usually use Newton’s Second Law of Motion to describe Momentum.

Study Guide- Chapter 9 Motion

Study Guide – Chapter 9 Motion

and Buoyancy

Key Terms are underlined and in bold. You need to know the definitions and examples/explanations for all key terms.

1. Buoyancy (pages 424 – 429)

A. Buoyancy is the ability to float

B. Buoyant Force is an upward force that is exerted by a fluid. Buoyant force acts in an opposite direction to gravity.

C. Archimedes’ Principle states that the buoyant force acting on a submerged object is equal to the weight of the volume of fluid displaced.

D. Be able to describe why a huge metal ship, like an aircraft carrier, is able to float, while a chunk of metal isn’t.

E. Be able to describe why the Titanic sank (or your overloaded aluminum foil boats) using density and buoyancy.

2. Describing Motion (Pages 338 – 341)

A. What is motion?

B. What is a reference point? Why is it important for the reference point to be a stable object?

C. If objects are moving together (like you when you drive home from school with your parents or a carpool) are they in motion relative to each other (relative motion)?

D. What are distance and displacement? Be able to label on a map.

3. Speed and Velocity (pages 342 – 347)

A. What is speed? Know that speed is calculated with the formula

speed = distance/time. Be able to solve speed problems.

B. Average speed is the total distance covered divided by the total time covered.

C. Velocity is speed in a direction. The formula for calculating velocity is the same as for speed but you need to add a direction.

D. Be able to read graphs showing Time and Distance like the graphs on pages 346 and 347. You need to be able to describe the motion at each point.

E. On distance and time graphs, the steeper the slope, the faster the object is moving. The shallower the slope, the slower the object is moving.

4. Acceleration (pages 352- 355)

A. Acceleration is the rate at which velocity changes. If speed changes (faster or slower) OR direction changes, then an object has accelerated.

B. Be able to read a distance vs. time graph for acceleration like the one on page 355.

C. IF I give you an extra credit questions, it may be to figure out the acceleration of an object given the velocities and total time like the zip line lab in class. See page 353 for practice.

5. Energy (pages 358 – 363)

A. Energy is the ability to do work. Work is what is required to put an object in motion.

B. Potential Energy is stored energy. Be able to describe chemical, elastic and gravitational potential energy in real-life situations.

C. Gravitational potential energy depends on the height of an object and its weight. The more massive the object and the height of the object will determine the amount of potential energy.

D. Kinetic Energy is energy of motion. As an object falls is gains kinetic as it loses potential. Energy is transformed. Kinetic energy depends upon mass and speed but speed really affects the moving energy of an object.

E. The Law of Conservation of Energy says that energy cannot be created or destroyed, it only changes form. Be able to apply this law to the roller coasters we build in class, to how a pendulum moves, and also to explain why the pendulum CAN’T hit you in the face if you let it go from the tip of your nose.

6. Review Concepts - Chapter 1 (pages 6-26)

I may ask questions about these concepts that have already been tested. You can use your old study guide (find a copy online) to get more information.

A. Scientific Equipment

B. Scientific Inquiry (Hypothesis, Manipulated /Independent Variable, Responding/Dependant Variable, Controlled Variables, Controlled Experiment, Scientific Theory)

C. Measurement – (Know the definitions and units used to measure mass, length, volume, and time.)

D. Know what density is and how it is different from weight. Additional information on density can also be found in the section with buoyancy (pages 424-429).

Kinetic and Potential Energy Homework

Name ____________________________

Kinetic and Potential Energy

Pages 358 – 363

1. What is energy?

2. What is kinetic energy?

3. What are the two things that affect the kinetic energy of an object?

A.

B.

4. What is potential energy?

5. What is gravitational potential energy? Give an example.

6. What kind of energy is shown when you stretch a rubber band?

7. How does a pendulum show the Law of Conservation of Energy?