PHYS 241 Practice Problems for Exam #1 PDF

PHYS 241 Practice Problems for Exam # 1 Name___________________________________ Section: _________________________________ TRUE/FALSE. Write 'T' if the statement is true and 'F' if th...

PHYS 241 Practice Problems for Exam # 1 Name___________________________________ Section: _________________________________ TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false. 1) A negative velocity, approaching zero, represents a negative acceleration. 2) If no force is applied to a moving object, it will continue to move with constant speed in a straight line. 3) The normal force is always equal to the force of gravity. 4) The vertical component of the acceleration of a projectile remains constant during the entire trajectory of the projectile. 5) The mass of an object is fixed, but its weight varies from location to location. 6) If an object’s speed is constant, then its acceleration must be zero. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 7) The slope of a line connecting two points on a velocity versus time graph gives A) average velocity. B) instantaneous velocity. C) instantaneous acceleration. D) average acceleration E) none of the given answers. 8) A pilot drops a bomb from a plane flying horizontally at a constant speed. When the bomb hits the ground, the horizontal location of the plane will A) be over the bomb. B) be in front of the bomb. C) be behind the bomb. 9) You are standing in a moving bus, and you suddenly fall backward. You can imply from this that the bus's A) velocity increased. B) the bus stopped. C) speed remained the same, but it's turning to the left. D) speed remained the same, but it's turning to the right. E) velocity decreased. 10) A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. A) The truck did not slow down during the collision. B) The force of collision on the truck is smaller than the of collision force on the car. C) The force of collision on the truck is equal to the force of collision e on the car. D) The force of collision on the truck is greater then the force of collision on the car. E) The car did not slow down during the collision. 11) If you run a complete loop around an outdoor track (400 m) in 100 s, your average velocity is A) 4.0 m/s. B) 0.25 m/s. C) zero. D) 40,000 m/s. E) 4.00 km/s. 1 12) The position, x , of an object is given by the equation x = A + Bt +Ct 2 , where t refers to time. What are the dimensions of A, B, and C? A) distance, time, time2 B) distance/time, distance/time2 , distance/time3 C) distance, time, time D) distance, distance, distance E) distance, distance/time, distance/time2 13) An object has a position given by r = [2.0 m + (5.00 m/s)t]i + [3.0 m - (2.00 m/s2 ) t 2 ]j. What is the ^ ^ magnitude of the acceleration of the object at time t = 2.00 s? A) 4.00 m/s2 B) 1.00 m/s2 C) 0.00 m/s2 D) 0.722 m/s2 E) 2.00 m/s2 FIGURE 4-13 14) A traffic light of weight 100 N is supported by two ropes as shown in Fig. 4-13. What are the tensions in the ropes? A) 83 N B) 56 N C) 66 N D) 63 N E) 50 N FIGURE 4-10 15) The three forces represented in Fig. 4-10 act on an object. What is the direction of the acceleration of the object? A) 78.7° counterclockwise from the +x-axis B) 11.3° clockwise from the +y-axis C) 11.3° counterclockwise from the +y-axis D) 11.3° clockwise from the -x-axis E) The mass of the object must be known to answer the question. 2 16) A jet fighter plane is launched from a catapult on an aircraft carrier. It reaches a speed of 42 m/s at the end of the catapult, and this requires 2 s. Assuming the acceleration is constant, what is the length of the catapult? A) 16 m B) 42 m C) 66 m D) 84 m E) 24 m FIGURE 2-8 17) Fig. 2-8 shows the velocity-versus-time graph for a basketball player traveling up and down the court in a straight-line path. Find the net displacement of the player for the 10 s shown on the graph. A) 16 m B) 20 m C) 18 m D) 12 m E) 14 m 18) A bullet shot straight up returns to its starting point in 10 s. Its initial speed was A) 32. ft/s. B) 98 m/s. C) 9.8 m/s. D) 49 m/s. E) 24.5 m/s. 19) Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s in 2.0 s. What is the net force acting on the body? A) 8.0 N B) 16 N C) 32 N D) 4.0 N E) 2.0 N FIGURE 4-11 20) A 6.00-kg block is in contact with a 4.00-kg block on a frictionless surface as shown in Fig. 4-11. The 6.00-kg block is being pushed by a 20.0-N force toward the 4.00-kg block. What is the magnitude of the force of the 6.00-kg block on the 4.00-kg block? A) 12.0 N B) 6.00 N C) 4.00 N D) 8.00 N E) 10.0 N 21) The velocity of a particle as a function of time is given by v (t ) = (2.3 m/s) + (4.1 m/s2 ) t - (6.2 m/s3 )t 2. What is the average acceleration of the particle between t = 1.0 s and t = 2.0 s? A) 15 m/s2 B) 0 m/s2 C) -13 m/s2 D) -15 m/s2 E) 13 m/s2 22) A child throws a ball with an initial speed of 8.00 m/s at an angle of 40.0° above the horizontal. The ball leaves her hand 1.00 m above the ground. How long is the ball in flight before it hits the ground? A) 6.79 s B) 7.45 s C) 2.44 s D) 9.14 s E) 1.22 s 3  23) A hockey puck slides off the edge of a table with an initial velocity of 26.0 m/s. The height of the table above the ground is 2.00 m. What is the angle below the horizontal of the velocity of the puck just before it hits the ground? A) 77.2° B) 13.5° C) 12.8° D) 31.8° E) 72.6° WRITTEN PROBLEMS (MUST SHOW YOUR WORK OTHERWISE NO CREDITS WILL BE GIVEN) FIGURE 4-7 24) Two boxes are connected by a cord running over a pulley as shown in Fig. 4-7. Box I of mass 8.0 kg rest on the top of the table; the coefficient of kinetic friction between box I and the table is 0.10. Box II has a mass of 15.0 kg. (a) Draw the free-body diagrams for the two boxes, identifying all of the forces acting on each of the masses. (b) Calculate the acceleration of the system. (c) Calculate the tension in the cord. 25) Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0-kg, 3.0-kg, and 2.0-kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two masses. (a) Draw the free-body diagrams for each of the masses. (b) What is the contact force between the 5.0-kg mass and the 3.0-kg mass? (c) What is the contact force between the 3.0-kg and the 2.0-kg mass? 26) A projectile is fired from ground level with an initial speed of 55.6 m/s at an angle of 41.2° above the horizontal. (a) Determine the time necessary for the projectile to reach its maximum height. (b) Determine the maximum height reached by the projectile. (c) Determine the horizontal and vertical components of the velocity vector at the maximum height. (d) Determine the horizontal and vertical components of the acceleration vector at the maximum height. 4