Physics Day 1—Units, Vectors, and Kinematics Units Velocity and Acceleration txv units are sm tva units are 2sm Force (Newtons) maF  22smkgsmkgN Energy/Work (Joules) FdW  22smkgmNJ 221mvKE  222smkgsmkgJ mghPE  222smkgmsmkgJ Power (Watts) tWP 3222smkgssmkgsJ  Density Vm units are 3mkg Pressure (Pascal) AFP  22smkgmNPa gDPfluid 223smkgmsmmkgPa SI Units Length m Mass kg Time s Electric current A Temperature K Luminous intensity Cd (candela) Derived Units Volume m3 Force N Energy/Work J Power W Pressure Pa Charge C Resistance  Capacitance FElectric Field Strength qEF  so qFE  units are CN (not usually broken down further but could be) Potential/Voltage (Volts) qVPE  so qPEV  3232sAmkgAsmkgAWCsWCJVolts Current (Ampere) tqI  sCAmps  Resistance (Ohms) IRV  so IVR  3223222222sAmkgsCmkgssCmkgCsJsCCJAV(a little tricky) Capacitance VQC  24222422222222mkgsAmkgssCmkgsCsmkgCJCCJCVCF (a little tricky) Magnetic Field Strength (Tesla) sinqvBF  so sinqvFB  sCkgmCssmkgmCsNsmCNT2 sinBIF  so sinIFB  sCkgmCssmkgmCsNmsCNmANT2Vectors Kinematics Displacement = Δx (change in position) or d (Difference from Distance) Velocity txv vavg = 2fivv  (Difference from Speed) Acceleration tva -acceleration due to gravity -acceleration while moving along a curve -signs () are important when displacement, velocity, and acceleration don’t all point in the same direction vtd  (no acceleration) tvdavg (constant acceleration) 221attvdi(constant acceleration) 221atd  when starting from rest advvif222(constant acceleration) used when no time information is available 1. A car accelerates from 40mph to 60 mph in 4 seconds. What is its acceleration? 2. A car travels north at 60mph for 5 hours. What is its total displacement? 3. From rest a car accelerates at 3m/s2. What is the car’s velocity after 6s? How far has it traveled? 4. A penny is dropped from the roof of a building and takes 4s to reach the ground. From what height was the penny dropped? (Ignore air resistance and use g=10m/s2) 5. A penny is dropped from the roof of a 100m tall building. How long does it take for the penny to reach the ground? (Ignore air resistance and use g=10m/s2) 6. A penny is dropped from a building. It’s final velocity just before it reaches the ground is 40m/s. From what height was the penny dropped?Graphs 7. Projectile Motion time to max height (tup) gvtyiup0 g = gravity max height (ymax) upyiupyavgtvtvy2max total time (ttotal) uptotaltt 2 horizontal displacement (x) totalxtvx  8. A potato is fired from a potato gun with an initial velocity of 100m/s 30 above the horizontal. What is the time of flight of the potato? What is its maximum height during flight? What is the distance between where it was fired and where it lands? 0 v t atvslope area = d Area = d 0 x t vtxslope  Graph A Graph BPhysics Day 2—Mechanics Newton’s Laws 1st Law – An object’s velocity remains constant unless a net force is acting upon it. If F=0, then v=constant 2nd Law – F=ma 3rd Law – For every force exerted by one object on a second object, there is an equal but opposite force by the second object on the first. 1221  FF 1. Two astronauts of masses 100kg and 150kg are at rest floating in space. The larger pushes the smaller so that they are moving away from each other. The 100 kg astronaut has a resulting acceleration of 2m/s. What was the force of the larger astronaut on the smaller astronaut? What was the resulting acceleration of the larger astronaut? Gravity W = mg 221rmmGFg 22111067.6kgmNxG For an object on the surface of the earth, mgrmMGFEEg2, so 228.9smrMGgEE 2. A new planet with twice the mass and a radius that is three times greater than that of earth has been discovered. How will its gravitational acceleration compare to that of earth? Normal Force – Perpendicular component of the contact force that a surface exerts on an object. Friction NkfFF kinetic NsfFFmax static 3. A 100kg man is on an elevator that is accelerating upward 2m/s2. What is his apparent weight? 4. A 10 kg object is being pulled horizontally along a surface with a force of 200N resulting in a net acceleration of 18m/s2. What is the coefficient of kinetic friction between the object and the surface?Inclines 5. A 10 kg object is at rest on a plane inclined 30 above the horizontal. What is the force of friction acting upon the object? What is the coefficient of friction (Be careful!)? 6. A 10 kg object slides down a frictionless plane inclined 30 above the horizontal. What is its acceleration? 7. An object slides down a 45 incline at constant velocity? What is the coefficient of kinetic friction between the object and the incline? Pulleys 8. For pulley 1, what is the tension in the rope if the mass is suspended at rest? 9. For pulley 2, what is the acceleration of the 7.5kg mass? 10. For pulley 3, what is the acceleration of the 7.5kg mass?Centripetal Force/Acceleration rvac2 cmarmvF 2 11. A boy is twirling a 100g yoyo with a 600cm radius horizontally in a circle above his head with a speed of 2m/s. What is the maximum centripetal force acting on the yoyo? 12. Give an expression for the radius of a satellite in a stable orbit around the Earth in terms of the gravitational constant G, the mass of the Earth ME, and the velocity v of the satellite. 13. A roller coaster car completes a loop-d-loop on it’s track. Is the normal force acting on the car by the track greater at the top or bottom of the loop-d-loop? By how much (answer in terms of m, v, r, and g)? Work and Energy FdW  (only force component in the direction of motion) 14. How much work is performed by an Alaskan husky pulling a dog sled 10m across the snow