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Transcript
Practice problems for st 1 exam 1) One car drives 45 m/s east, another car drives 45 m/s north. Do the 2 cars have the same velocity? Yes or No 2) Cars 1 and 2 leave Johnson City at the same time. Car 1 drives straight to Nashville. Car 2 drives to Chattanooga and then to Nashville, but arrives at Nashville at the same as Car 1. Do the cars have the same average speed? a) Yes b) No Do the cars have the same average velocity? a) Yes b) No 3) Ball 1 is thrown horizontally from a 2 m ledge at the same time Ball 2 is dropped from the ledge. Which ball reaches ground first? a) Ball 1 b) Ball 2 c) land at same time 4) A driver driving on a circular track notices that the speedometer stays constant. Is the car accelerating. a) Yes b) No 5) Circle the object that has the most inertia. a) train b) cat 6) A Puma starting from rest can reach 20 m/s in a 4 second interval. What is the puma’s acceleration? a) 4m/s2 b) 5m/s2 c) 9.8m/s2 d) 10m/s2 7) Which quantities are scalars? a) mass b) force c) speed d) velocity 8) Which speed is higher? a) 10 km/hr b) 10 m/s e) time 9) A ball is thrown at an angle. The x component of velocity is a) constant b) varies The y component of velocity is a) constant b) varies 10) What force is needed to give a 2 kg mass an acceleration of 8 m/s2? a) 4 N b) 8 N c) 16 N d) 32 N 11) Convert 35 kg/m3 to a density in g/cm3. 12)Convert 45 miles per hour to a velocity with units m/s. 13) A force vector has components Fx = 3 N, and Fy = 4 N. What is the force’s magnitude? a) 3 N b) 4 N c) 5 N d) 7 N 14) A 5 kg cat sleeps on a window sill, what normal force is supporting the cat? a) 5 N b) 9.8 N c) 49 N 15)A bomb is dropped from a stationary helicopter hovering 250 m above the ground. a) How much time is the bomb in the air? b) What is the bomb’s speed when it hits he ground? 16)A cannonball is fired from ground level with a velocity of 20 m/s at an angle of 30 degrees above horizontal. A) How far will the cannonball travel? B) How high is the cannonball at its highest point? C) What is the cannonball’s speed at the highest point? 17) A puma jumps horizontally from a 2 meter high tree limb in hopes to land on a deer standing 5 meters horizontally away from the tree. With what velocity must the puma jump from the limb to reach the deer? 18) A ball is thrown from a 20 meter high building, with a velocity of 10 m/s at an angle of 30 degrees above horizontal How far from the building, will the ball land? 19) A 1500 kg car is driving 30 m/s. The brakes are applied and the car comes to a stop over a 50 meter distance. What force did the brakes exert on the car? 20)A box slides down a 30 degree incline with a constant velocity. What is the coefficient of kinetic friction? 21) A person want to place a box on a 50 degree incline. What coefficient of friction is needed to keep the box from sliding? 22)A person want to drag a 20 kg sled over a flat field. The person pulls on the rope horizontally, and the coefficient of kinetic fiction is 0.6. a) With what force must the person pull to keep the sled moving with a constant velocity? b) With what force must the person pull to give the sled an acceleration of 2 m/s2? 23) The coefficient of static friction between a 2 kg book and a wall is 0.4. With what force must a person press the book into the wall to keep it from falling? 24) Three forces are applied to a 5 kg box as shown in the picture. What is the box’s acceleration vector? y (10 N, 30o) x (5 N, -900)