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Happy Monday! 1. Grab your calculator 2. Get ready for warm up #5 3. Turn in your “One Pager” assignment 4. Test review is worth a grade Test tomorrow!! Warm up # 5 Assume a 15 kg object is moving at the acceleration in the graph above. What force is required to make the object move at the acceleration in the graph? Forces and Newton’s Laws Formulas F= ma F f = m FN Quick review • • • • NET force, or FNET = total amount of force if two forces are in the same direction, add If they are pulling in opposite direction, subtract Types of forces: FWEIGHT FTENSION, FPUSH, FPULL, FNORMAL, FFRICTION, FTHRUST • You only have 2 equations: 1. F= ma 2. Ff = m (m)(g) Name those units! What are the units for force? Newtons What are the units for mass? Kilograms What are the units for weight? Newtons What are the units for acceleration? m/s2 What are the units for velocity? m/s What is the SYMBOL for the coefficient of friction? m . Identify each of the following as: FWEIGHT FTENSION, FPUSH, FPULL, FNORMAL, FFRICTION Placing a heavy object on a table FWEIGHT The table pushes back against the object FNORMAL Bicycle brakes FFRICTION Playing tug of war FTENSION Your friend shoves you FPUSH Check Your Understanding 1. What acceleration will result when a 12 N net force applied to a 3 kg object? 4 m/s2 2. A net force of 16 N causes2 a mass to accelerate at a rate of 5 m/s . Determine the mass. 3.2 kg 3. How much force is needed to accelerate a 66 kg skier 1 m/sec/sec? 66 N 7 Which has more inertia? Bicycle or car? Basketball or golfball? INERTIA = MASS WEIGHT AND THE NORMAL FORCE • Weight is defined as mass being accelerated towards the Earth by gravity (9.8 m/s2) • What is the formula for determining the weight of something? • FWEIGHT = m (9.8) • What is the NORMAL FORCE, or FNORMAL , almost always equal to? • WEIGHT FORCE, or FWEIGHT WEIGHT AND THE NORMAL FORCE What is FWEIGHT ? What is FNORMAL? 118 N 12 kg 118 N Check your understanding Jennifer has a mass of 48 kg. What is her weight in Newtons? 470 N A book that has a weight of 42 N is resting on the table. What is the normal force? (FNORMAL or FN) 42N Calculate the normal force! 157 N FWEIGHT = 6 x 9.8 = 58.8 N + 10.0N 69 N What is the NET force? 5 N to the left 0N What is the Normal force equal to? FWEIGHT Calculate Acceleration 10m/s2 0.27 m/s2 Calculate the following What is the magnitude of the friction force if a sled has a mass of 78 kg coefficient of friction is 0.15? 115 N Find the friction force if a boy on ice skates has a mass of 80 kg and the coefficient of friction is .08. 63 N Calculate the following: A huge pile of leaves was wrapped in a tarp in the middle of a lawn. The wrapped leaves weigh 880 N. The coefficient of friction for the lawn is 0.55. Find friction force. Remember: Ff = m(FN) 484 N A car got stuck in the mud. Two boys attached ropes and tried to pull the 3000 kilogram car out. One boy pulls to the left with a force of 250 N and the other boy pulls in the same direction with a force of 280 N. Draw a free body diagram of scenario above. The coefficient of friction is 0.60. Calculate the forces acting upon the car 29,400N 530N 1800N What is the NET force acting upon the car? 29,400N 1270N to the right Will the boys be able to pull the car out? No, they must exert more force