By Bryan Tran and Cooper Schultz Physics Review By Bryan Tran and Cooper Schultz

Scientific Method Have a question Make a prediction/ hypothesis Conduct an experiment Present your results ( graphs, tables) Analyze results- compare results with predictions Change your original thinking or keep your ideas A Good Experiment A testable question Only one independent variable Clear instructions Multiple trials Minimize errors Example A man has a question. He makes a prediction, does an experiment, presents his results with graphs and tables. He then compares his results with his predictions and finds out his prediction was wrong.

Motion Graphs The person is in the helicopter on the ground The helicopter rising The helicopter goes up from being on the ground Helicopter rising then stopping at drop off height The skydiver hits terminal velocity Skydiver jumps out of helicopter Skydiver pulls parachute

Calculations Avg velocity = delta distance/time Skydiver drops a distance of 5500m in 350s. 5500/350 = 15.7m/s Instantaneous Velocity = Avg velocity*2 Skydiver’s average velocity at 10s is 25m/s. 25*2 = 50m/s Acceleration = delta velocity/time Skydiver’s speed changes from 30m/s to 10m/s in 20s (10-30)/20 = -1m/s^2

Newton’s First Law When forces are balanced, there is no net force, and the object is still or has uniform velocity. When forces are unbalanced, there is net force. Acceleration is speeding up, slowing down, or changing direction. Ex.- if a skydiver is falling out of a helicopter, he accelerates, putting a net force on himself. Eventually he reaches constant velocity, making the forces on him balanced.

Free Body Diagrams

Newton’s Second Law Fnet=m*a (net force equals mass times acceleration) Ex.- calculate the net force on the skydiver if his mass is 70 kg and his acceleration is 10 m/s squared Fnet=m*a Fnet=70 kg* 10 m/s squared Fnet=700 Newtons

Newton’s Third Law For every force, there is an equal force in the opposite direction. The forces are on two different objects and do not cancel each other out. When the skydiver lands on the ground, the ground impacts a force on the person. At the same time, the person impacts a force on the ground of the same magnitude.

Weight Weight= force of gravity. W= Fg Weight is the force with which earth attracts an object Mass is the amount of material in an object and measures the object’s inertia or resistance to change in motion. Fg= m* 9.8 m/s squared. Fg= m* g Ex.- a skydiver’s mass is 68 kg. 68*10 = 680N

Law of Gravitation A force of attraction exists between any two objects. Because of Newton’s third law, this force is the same on each object. The force of gravity increases as the mass of either object increases. The force of gravity decreases as the distance between the objects increases Fg= G m1* m2/ d squared Ex.- if a skydiver is diving towards the earth there is an equal force on the earth and the diver.the force weakens as they move apart and gets stronger as they move together.

Momentum, Impulse, Collision Momentum = mass*velocity Skydiver's mass is 68kg falling at 25m/s. 68*25 = 1700kgm/s Impulse = force*time The force on the skydiver is 7N for 5s. 7*5 = 35Ns Collision: m1*v1 + m2*v2 = m1*v1 + m2*v2 Skydiver of 68kg has a horizontal velocity of 2m/s. A ball of 1kg has a horizontal velocity of 0m/s. The skydiver has a horizontal velocity of 1m/s after colliding with ball. 68*2+1*0 = 68*1+1*1 The horizontal velocity of the ball is now 68m/s

Energy (GPE, KE) Energy is the ability to create change or do work Energy comes in different forms and can be transformed (changed) from one form to another. Total energy of a closed system is always conserved. Gravitational potential energy (GPE) GPE= m*g*h (mass times gravitational acceleration times height) Kinetic Energy (KE) KE=1/2mv squared (one half mass times velocity squared) Ex.- if a skydiver’s mass is 70 kg, and he is 500 m off the ground, his GPE IS 350,000 joules. 70*10*500= 350,000 j If that same diver’s mass is 70 kg and his velocity is 25 m/s, his KE is 21875 joules ½*70*25 squared= 21875 j

Thermodynamics Thermal energy is the kinetic energy of particles in an object. Thermal energy (kinetic) is measured by the temperature of the object. When the temperature rises in a closed system, the pressure increases. Thermal energy will only flow from high temperature to low temperature. As the skydiver falls, air resistance increases and in turn making the skydiver’s temperature increase showing that their GPE has turned into KE and thermal energy.