Download Study Guide - Forces and Newton`s Laws

7th GRADE SCIENCE
STUDY GUIDE
*** Motion, Forces and Energy: Book “M”: ***
Chapter Two: Forces and Newton’s Laws
- given a description of an event, identify which of Newton’s laws is illustrated,
and explain (pp.36-54)
Section One:
Newton’s First Law: pp. 36-41
- define force (p.36)
- distinguish between balanced and unbalanced forces (p.37)
- state Newton’s first law (p.38)
- give an example of Newton’s first law (p.38)
- describe the differences among static, sliding and rolling friction (pp.40-41)
- explain how friction affects motion (pp.38-41)
Section Two:
Newton’s Second Law: pp.42-48
- describe the difference between mass and weight (pp.43-44)
- state Newton’s second law (p.42)
- give an example of Newton’s second law (p.42)
- describe how the mass of an object affects the acceleration for a given force (p.42)
- describe how the direction of a force acting on an object affects its motion (pp.44-47)
- explain why an object in circular motion at a constant speed is accelerating (pp.46-47)
- describe how a force can keep an object in circular motion (pp.46-47)
Section Three: Newton’s Third Law: pp.49-54
- state Newton’s third law (p.49)
- give an example of Newton’s third law (p.49)
Correlates to Pennsylvania Department of Education Assessment Anchor S8.C.3
*** Motion, Forces and Energy: Book “M”: ***
Chapter Two: Forces and Newton’s Laws
Section One: Newton’s First Law: pp. 36-41
- A force is a push or a pull.
- The combination of all forces acting on an object can be balanced or unbalanced.
If the forces are balanced, the net force is zero.
- If the net force on an object at rest is zero, the object remains at rest, or
if the object is moving, it continues moving in a straight line with a constant speed.
- Friction is the force that acts to resist sliding between two surfaces that are touching.
- There are three types of friction:
- static friction is the resistance force that keeps an object at rest from sliding;
- sliding friction is the resistance force that keeps a sliding object from sliding easily;
- rolling friction is the force that keeps a rolling tire from slipping on the ground.
Section Two:
Newton’s Second Law: pp.42-48
- Mass is the amount of matter in an object; weight is how much gravity pulls on that mass.
- Newton’s second law states that an object acted upon by a net force will accelerate in the
direction of the force.
- Force, mass, and acceleration are related by the following equation:
force
=
mass
X
acceleration
- For a given force, the bigger the mass, the smaller the acceleration.
- The direction of a force acting on an object affects its motion. A moving object:
- speeds up, if the net force is in the direction of the motion.
- slows down, if the net force is in the opposite direction to the motion.
- turns, if the net force is at an angle to the direction of the motion.
- An object traveling in a circle at a constant speed is accelerating, because the direction is
changing. Acceleration is a change in velocity, and direction is a part of velocity.
- A force acting toward the center of a circle keeps an object moving in circular motion.
Section Three: Newton’s Third Law: pp.49-54
- According to Newton’s third law, the forces two objects exert on each other are always
equal, but in opposite directions.
- Action and reaction forces don’t cancel because they act on different objects.