Warm-Up: Energy Review Answer the questions below. Answer the questions below

Where does the car have the most potential energy? 1. Between A and B 2. Between B and C 3. Between C and D 4. After D

Where does the car have more kinetic energy than potential? 1. A 2. B 3. C 4. D

Force & Motion

Motion Speed = rate at which an object moves Speed = rate at which an object moves

Motion speed equation: speed = distance ÷ time (v = d ÷ t) units of speed: meters per second (m/s) or kilometers per hour (km/hr)

Example: A jogger runs the first 1000 m of a race in 250 sec. What is the jogger’s speed? What is the correct way to plug in the numbers? 1. v = 250 sec ÷ 1000 m 2. v = 1000 m ÷ 250 sec 3. v = 1000 m x 250 sec 4. v = 250 sec x 1000 m

Motion Speed = rate at which an object moves Speed = rate at which an object moves speed = distance ÷ time (v = d ÷ t) Example: A jogger runs the first 1000 m of a race in 250 sec. What is the jogger’s speed? v = 1000 m ÷ 250 sec.

Example: A jogger runs the first 1000 m of a race in 250 sec. What is the jogger’s speed? m/sec sec/m 3. 4 m/sec 4. 4 sec/m

Motion Speed = rate at which an object moves Speed = rate at which an object moves speed = distance ÷ time (v = d ÷ t) Example: A jogger runs the first 1000 m of a race in 250 sec. What is the jogger’s speed? v = 1000 m ÷ 250 sec. v = 4 m/sec.

Motion Speed = rate at which an object moves Speed = rate at which an object moves Velocity = speed with a specific direction Velocity = speed with a specific direction

Example: A running back moves towards the east end zone at 10 m/sec. What is the running back’s velocity? m/sec m/sec west m/sec east meters east

Motion Speed = rate at which an object moves Speed = rate at which an object moves Velocity = speed with a specific direction Velocity = speed with a specific direction Example: A running back moves towards the east end zone at 10 m/sec. –What is the running back’s velocity? velocity = 10 m/sec. east

Motion Acceleration = change in velocity Acceleration = change in velocity

Motion –Acceleration can mean: Speeding up Speeding up

Motion Acceleration = change in velocity Acceleration = change in velocity –Acceleration can mean: Speeding up Speeding up Slowing down Slowing down

Motion Acceleration = change in velocity Acceleration = change in velocity –Acceleration can mean: Speeding up Speeding up Slowing down Slowing down Changing direction Changing direction –Think of a rollercoaster because it can do all three!

Which car is not accelerating? 1. A car driving up a hill and down the other side. 2. A car turning a corner. 3. A car turning a corner at a constant speed. 4. A car driving at a constant speed along a straight highway.

Which is NOT an example of acceleration? 1. As you see your friend, you jump up and run to greet them. 2. Your dog runs in circles chasing his tail. 3. You pedal your bike along your street at 5 km/hr. 4. A car slows down as it comes to a red light.

Motion Acceleration = change in velocity Acceleration = change in velocity acceleration equation: acceleration = velocity ÷ time (a = v ÷ t) units of acceleration: m/s per second (m/s 2 ) or km/hr per hour (km/hr 2 )

Example: A car accelerates from 0 to 72 km/hr in 8 sec. What is the car’s acceleration? What is the correct way to plug in the numbers? 1. a = 72 km ÷ 8 sec 2. a = 0 km/hr ÷ 8 sec 3. a = 72 km/hr ÷ 8 sec 4. a = 8 sec ÷ 72 km/hr

Motion Acceleration = change in velocity Acceleration = change in velocity acceleration = velocity ÷ time (a = v ÷ t) Example: A car accelerates from 0 to 72 km/hr in 8 sec. What is the car’s acceleration? a = 72 km/hr ÷ 8 sec.

Example: A car accelerates from 0 to 72 km/hr in 8 sec. What is the car’s acceleration? 1. 9 km/hr 2. 9 km/hr/sec 3. 9 km/hr/hr 4. 9 km

Motion Acceleration = change in velocity Acceleration = change in velocity acceleration = velocity ÷ time (a = v ÷ t) Example: A car accelerates from 0 to 72 km/hr in 8 sec. What is the car’s acceleration? a = 72 km/hr ÷ 8 sec. a = 9 km/hr/s

Force Force = a push or a pull Force = a push or a pull

Force –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

Force 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 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 force on rope = 20 N to the right Rope’s moves to the right (it is in disequilibrium)

Which box is experiencing unbalanced forces? 5 N 10 N 1. Box A 2. Box B 3. Box C 4. Box D A 5 N 10 N B C D 5 N

What will Box D do? 5 N 10 N D 5 N 1. Accelerate to the left 2. Accelerate to the right 3. Stay still 4. 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? 1. Downward force of gravity 2. Backward force of friction 3. Upward force of the counter 4. 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)

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? 1. When driving on the highway 2. When walking across a wet floor 3. When snowboarding in the Olympics 4. When climbing a steep hill

How could you increase friction? 1. Polishing metal surfaces 2. Adding oil to the gears on a bike 3. Wearing slick shoes 4. 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 gravity Air resistance

When dropped, which object would experience the MOST air resistance? 1. A flat sheet of paper 2. A wadded up sheet of paper 3. A paperclip 4. A tennis ball