Forces

Between which 2 points is the turtle accelerating? a) A & B b) B & C c) A & C d) B & D

Between which 2 points is the turtle staying still? a) Before A b) B & C c) Before A and between B & C d) The turtle does not stay still

Forces Affect Motion Force = a push or a pull Force = a push or a pull

Forces Affect Motion Force = a push or a pull Force = a push or a pull –forces have a strength and direction –Forces are measured in units called Newtons (N) 1 N 20 N Small force pushing to the right Big force pushing to the left

Forces Affect Motion Balanced forces = equal forces working on 1 object in opposite directions Balanced forces = equal forces working on 1 object in opposite directions 100 N Total (net) force on rope = 0 N Rope’s motion does not change (it is in equilibrium) -

Force Unbalanced forces = unequal forces cause an object to accelerate Unbalanced forces = unequal forces cause an object to accelerate 120 N100 N Total (net) force on rope = 20 N to the right Rope moves to the right (it is in disequilibrium) -

Which box is experiencing unbalanced forces? 5 N 10 N A 5 N 10 N B C D 5 N a) Box A b) Box B c) Box C d) Box D

Which boxes have a total (net) force of 0 N acting on them? 5 N 10 N A 5 N 10 N B C D 5 N a) A only b) A & B c) A & C d) A, B & C

What is the total (net) force acting on Box D? 5 N 10 N D 5 N a) 20 N to the right b) 20 N to the left c) 10 N to the right d) 10 N to the left

What will Box D do? 5 N 10 N D 5 N a) Accelerate to the left b) Accelerate to the right c) Stay still d) Explode

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object

Which force is acting on the ball rolling across the counter? a) Downward force of gravity b) Backward force of friction c) Upward force of the counter d) All of these forces are acting on the ball

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Friction = force exerted when 2 surfaces rub against each other

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Friction = force exerted when 2 surfaces rub against each other Sliding = solid surfaces slide over each other Sliding = solid surfaces slide over each other motion friction

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Friction = force exerted when 2 surfaces rub against each other Sliding Sliding Rolling = object rolls over a solid surface Rolling = object rolls over a solid surface F M

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Friction = force exerted when 2 surfaces rub against each other Sliding Sliding Rolling Rolling Fluid = object moving Fluid = object moving through a fluid (liquid or gas) M F

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Friction Sliding Sliding Rolling Rolling Fluid Fluid –Force of friction depends on: types of surfaces types of surfaces how hard the surfaces push together how hard the surfaces push together

When might you want to decrease friction? a) When driving on the highway b) When walking across a wet floor c) When snowboarding in the Olympics d) When climbing a steep hill

How could you increase friction? a) Polishing metal surfaces b) Adding oil to the gears on a bike c) Wearing slick shoes d) Putting sand on an icy driveway

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Gravity = force that pulls objects toward each other

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Gravity = force that pulls objects toward each other –Force of gravity depends on: objects’ mass objects’ mass distance between distance betweenobjects

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Air resistance = a type of fluid friction that affects falling objects gravity Air resistance

Resistance Forces Resistance forces = forces that go against the motion of an object Resistance forces = forces that go against the motion of an object –Air resistance = a type of fluid friction that affects falling objects –Force of air resistance depends on: Object’s surface area Object’s surface area Object’s speed Object’s speed Skydiving video clip gravity Air resistance

When dropped, which object would experience the MOST air resistance? a) A flat sheet of paper b) A wadded up sheet of paper c) A paperclip d) A tennis ball