PHY211 General Physics I Ch 6 Worksheet Force and Motion II page 1 of 7 PCC Cascade 1 The motion of a 0 1 kg ball tossed vertically into the air was recorded using a motion detector The initial velocity for the ball was 5 m s see Graph 1 Analysis of the velocity vs time graph yielded the acceleration of the ball during 3 phases of the motion upward near the top and downward Graph 2 During the upward movement the average acceleration aupward is 12 3 m s2 Near the top of the trajectory where air drag was minimal the average acceleration of the ball is 10 1 m s2 why is it not 9 8 m s2 During the descent the average acceleration adownward is 7 8 m s2 Problems a Observing Graph 1 how does air drag affect shape of the velocity vs time graph i e the motion of the ball compared to no drag b Why is the upward acceleration of the ball near the launch greater than at the top or during the descent c Sketch a force vector diagram for each phase of the ball s motion Upward At the top Downward d Using your force diagrams as reference apply Newton s 2nd Law of motion to the ball for each phase Upward At the top Downward e Determine the average force vector of air drag in component form on the ball for each phase Upward At the top Downward f For each phase identify the action reaction forces that act on the ball Upward At the top Downward PHY211 General Physics I Ch 6 Worksheet Force and Motion II page 2 of 7 PCC Cascade Graph 1 Comparison of a tossed ball with triangles and w o circles air drag Graph 2 Graphical analysis of the phases flight for a vertically tossed ball PHY211 General Physics I Ch 6 Worksheet Force and Motion II page 3 of 7 PCC Cascade 2 A 50 kg box is pulled horizontally along a floor against a 30 N kinetic friction force The observed net force acting on the box is 100 N a Draw a free body diagram for the box b What is the magnitude and direction of the net force Fnet acting on the box d What is the magnitude and direction of the friction force exerted on the box Determine the coefficient of kinetic friction k e What is the acceleration of the box in component vector form and how far does the box travel in 2 5 seconds 3 The 50 kg box is pulled up a 30o incline by a 1000 N force against a kinetic friction force The coefficient of kinetic friction between the box and the inclined plane is k 0 25 a Draw a free body diagram for the box b What is the frictional force expressed as a vector acting on the box c What is the magnitude and direction of the net force Fnet acting on the box d What is the magnitude and direction of the acceleration vector for the box e How long does it take to pull the box 2 0 m up the incline PHY211 General Physics I Ch 6 Worksheet Force and Motion II page 4 of 7 PCC Cascade 4 A Corvette convertible mass 1581 8 kg accelerates in a straight line from 0 to 60 mph with an elapsed time of 5 5 s on a flat level track The tires never lose traction with the road surface a Draw a free body diagram for the Corvette during this road test b What is the weight of the Corvette c Apply Newton s 2nd Law to the Corvette What is the direction and magnitude of the average net force exerted on the Corvette d What is the minimum coefficient of static friction required to keep the Corvette tires gripped to the track surface 5 A 2 kg block is supported by a flat wooden platform The platform has an adjustable incline that can be raised from 0o to 90 o with respect to the horizontal direction The coefficient of static friction between the block and the platform surface is 0 5 a As the platform is raised to some angle draw the free body diagram for the block as it sits at rest on the incline 2 kg b Apply Newton s 2nd Law to the block described in part a What is the direction and magnitude of the net force exerted on the block as a function of the incline angle c Determine the maximum angle that the incline can be raised before the block will begin to slide d What is the magnitude of the normal force at the angle determined in part c e What is the magnitude of the maximum static friction force acting on the block in part c PHY211 General Physics I Ch 6 Worksheet Force and Motion II page 5 of 7 PCC Cascade 6 Consider the following pulley system where there is friction static and or kinetic between M2 and the horizontal surface M2 a Draw free body diagrams for each mass b Apply Newton s 2nd law in vector form to each mass M1 c Determine an equation for the acceleration vector for each mass in terms of only the masses k and g d If M1 10 kg and M2 20 kg what is the minimum static friction coefficient that will keep the system from moving 7 Joey 60 kg jumps out of an airplane and plummets to the ground Descending in spread eagle fashion area 0 5 m2 he reaches a terminal velocity of 120 miles hour Assume the air density air is 1 10 kg m3 a Draw a free body diagram for Joey during his fall b What is the terminal velocity in SI units c Apply Newton s 2nd Law to our intrepid skydiver at terminal velocity What is the coefficient of drag for Joey during the descent d Getting cocky Joey quickly flips into a nose dive decreasing his effective surface area to 0 2 m2 What is Joey s new terminal velocity e What is the net force exerted on Joey the moment just after he flips into the nose dive f Finally Joey pulls his parachute cord and the parachute rapidly opens cross sectional radius 5 m What is Joey s terminal velocity with the open chute assuming he has enough time to reach it prior to hitting the ground PHY211 General Physics I Ch 6 Worksheet Force and Motion II page 6 of 7 PCC Cascade 8 Lateral Acceleration Centripetal Force According to Road Track magazine the maximum lateral acceleration of the Corvette Convertible mass 1581 8 kg is 0 98 g gravitational acceleration not grams To measure lateral acceleration the Corvette is driven around a flat 200 ft radius track the skidpad at the highest speed possible until the tires lose grip with the road a Draw a simple free body diagram for the car b What speed would correspond to the centripetal acceleration measured above b c Determine the magnitude of centripetal force vector exerted on the …