Acceleration and Motion

Section 4.1 Accelerated Motion

l Newton’s Second Law: a net force acting on an object causes the object to accelerate in the direction of force.

¡Depends on the size of force and mass of object (Force = mass x acceleration)

^¡ Measured in kg x m/s² (1 N = 1 kg x m/s² )

4.1 continued

l Falling Objects: even if objects are different in mass; they will accelerate due to gravity at the same rate.

^¡ For earth a = 9.8 m/s²

¡ Air resistance effects the rate of fall

¡ Air resistance depends on speed, size, shape, and density of the object.

l Terminal Velocity: the highest velocity that will be reached by a falling object

¡ As objects fall the increase in acceleration until they forces of inertia are balanced with gravity and the object will stop accelerating

Section 4.2: Projectiles and Circular Motion

l Projectiles: any object thrown or shot through the air

¡ Follow a curved path due to gravity

¡ Projectiles will land at the same time as dropped objects

4.2 continued

l Moving in Circles: involves objects traveling in curved paths

¡ Centripetal acceleration: acceleration toward the center of a curved or circular path

¡ Centripetal force: force acting on the object that causes a moving object to move in curved path

4.2 cont.

l Weightlessness in Orbit:

¡For true weightless to occur you must not have gravity effecting the object

¡Apparent weightlessness occurs when objects are in “free fall” with the exact rate of acceleration as gravity. (imagine riding in a super fast elevator)

Section 4.3: Science & Society

l Effects of Weightlessness

¡ Weakening of heart and bones

¡ Can be lessened by isometric exercises

Section 4.4: Action and Reaction

l Newton’s Third Law: when an object exerts a force on a second object, the second object exerts a force that is equal and opposite to the first object

¡Every action there is an equal and opposite reaction

¡Example: gun recoil, balloon, leaping from a boat

4.4 continued

lRocket Propulsion: works on the principle of Newton’s 3^rd law

4.4 cont.

l Momentum: a property a moving object has due to its mass and velocity

¡Momentum (p) = mass (m) x velocity (v)

¡Units are kg x m/s

¡Depends on the mass of the object

¡Momentum is continuous unless gravity acts on it