Motion and Forces

1. Newton’s laws predict the motion of most objects. As a basis for understanding this
concept:
a. Students know how to solve problems that involve constant speed and average
speed.
b. Students know that when forces are balanced, no acceleration occurs; thus an
object continues to move at a constant speed or stays at rest (Newton’s first law).
c. Students know how to apply the law FÊ=Ê ma to solve one-dimensional motion
problems that involve constant forces (Newton’s second law).
d. Students know that when one object exerts a force on a second object, the second
object always exerts a force of equal magnitude and in the opposite direction
(Newton’s third law).
e. Students know the relationship between the universal law of gravitation and the
effect of gravity on an object at the surface of Earth.

1. Newton’s laws predict the motion of most objects. As a basis for understanding this
concept:
a. Students know how to solve problems that involve constant speed and average
speed.
b. Students know that when forces are balanced, no acceleration occurs; thus an
object continues to move at a constant speed or stays at rest (Newton’s first law).
c. Students know how to apply the law FÊ=Ê ma to solve one-dimensional motion
problems that involve constant forces (Newton’s second law).
d. Students know that when one object exerts a force on a second object, the second
object always exerts a force of equal magnitude and in the opposite direction
(Newton’s third law).
e. Students know the relationship between the universal law of gravitation and the
effect of gravity on an object at the surface of Earth.
f. Students know applying a force to an object perpendicular to the direction of its
motion causes the object to change direction but not speed (e.g., Earth’s gravitational
force causes a satellite in a circular orbit to change direction but not speed).
g. Students know circular motion requires the application of a constant force directed
toward the center of the circle.
h.* Students know Newton’s laws are not exact but provide very good approximations
unless an object is moving close to the speed of light or is small enough that
quantum effects are important.
i.* Students know how to solve two-dimensional trajectory problems.
j.* Students know how to resolve two-dimensional vectors into their components and
calculate the magnitude and direction of a vector from its components.
k.* Students know how to solve two-dimensional problems involving balanced forces
(statics).
l.* Students know how to solve problems in circular motion by using the formula for
centripetal acceleration in the following form: aÊ=Êv2/r.
m.* Students know how to solve problems involving the forces between two electric
charges at a distance (Coulomb’s law) or the forces between two masses at a
distance (universal gravitation).