MOTION

d

s t

Average speed = change in distance change in time

S = Δd / Δt

Velocity includes speed and direction!!

Speed constant…velocity changing…acceleration changing

Δv

a Δt

Acceleration = final velocity - initial velocity final time - initial time

a = Δv/Δt

Newton’s 1st Law of Motion

An object at rest remains at rest unless acted upon by an unbalanced net force

orAn object moving at a constant velocity continues to

move at that velocity unless acted upon by an unbalanced net force

Forces4 Basic Forces: gravity, strong nuclear force, weak nuclear force, electromagnetic force

Newton’s 2nd Law of MotionAn object’s acceleration is in the same direction as the

net force acting upon it

Acceleration(m/s2) = net force(N)/mass(kg)

a = Fnet / m

Law of Universal Gravitation

Find the force of gravity between 2 objects, if masses and distance between them are known

Gravitational = (constant) x (mass1)x(mass2) force (distance)2

F = G m1m2

d2

Note force changes as mass and distance changes!

Force of Earth’s Gravity and an object’s Weight on Earth

Force of = mass(kg) x acceleration of gravity(N) gravity (9.8m/s2)

F = mg

Weight on = mass(kg) x acceleration of Earth gravity(9.8m/s2)

W = mg

An Object’s Weight on Earth is the Force of Gravity acting upon that object!!

Newton’s 3rd Law of MotionWhen one object exerts a force on a second object,

that second object exerts a force that is equal in strength, and opposite in direction

orFor every action force, there is an equal and

opposite reaction force

F1

Dir 1

F2

Dir 2

The skater throws the ball with force F1 in the direction Dir 1; The ball exerts a force F2 on the skater, who moves in the opposite direction Dir 2

Law of Conservation of Momentum

If a group of objects exerts forces only on each other, the total momentum is conserved

M3

M1 v1 M1 v1’

M2

v3

v2

M1V1 = M1V1’ + M2V2 + M3V3

WorkW(Nm) = F(N) x d(m)

d1

d2

F1

F2

How do the distances d1 and d2 compare? F1 and F2?

How does the work to move the object from floor to shelf by direct lifting compare to that by using the ramp?

Is there any advantage to using the ramp?

Mechanical Advantage

Mechanical Advantage = Force (out) / Force (in)

MA = Output Force = Lift Force (no ramp) Input Force Force with ramp

POWER

Power = rate of Energy Use= rate of Work completion

Power (Watts) = Energy (Joules) Time (s)

P = E/t = W/t