What part has zero acceleration? Where is the object stationary? Is there a region of constant acceleration?

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1 What part has zero acceleration? Where is the object stationary? Is there a region of constant acceleration?

2 What part has zero acceleration? Only if not turning Where is the object stationary? Is there a region of constant acceleration?

3 What force does air resistance exert on the skydiver? The skydiver then pulls his parachute at an altitude of 860 m and drops to the ground according to: y=860 m (50 m/s t) + (0.025 m/s 3 t 3 ) a. Find velocity and acceleration 20 seconds later. b. Draw an accurate force diagram for this time.

4 You fire a water balloon from the ground with an initial velocity of v o at an angle θ from the horizontal. The balloon is aimed at a window at height D, and the distance to the building is also D. If air resistance is neglected, find the firing angle needed if the balloon is to hit your friend head on, with zero vertical component of the velocity.

5 You are bicycling toward a building at speed v o /2, and fire a water balloon from ground level with an initial velocity of v o at an angle θ from the horizontal, relative to you. The balloon is aimed at a window at height D, and the distance to the building is also D at time of firing. If air resistance is neglected, find the firing angle needed if the balloon is to hit your friend head on, with zero vertical component of the velocity.

6 Q4.3 The graph to the right shows the velocity of an object as a function of time. Which of the graphs below best shows the net force versus time for this object? 0 v x t ΣF x ΣF x ΣF x ΣF x ΣF x 0 t 0 t 0 t 0 t 0 t A. B. C. D. E.

7 A4.3 The graph to the right shows the velocity of an object as a function of time. Which of the graphs below best shows the net force versus time for this object? 0 v x t ΣF x ΣF x ΣF x ΣF x ΣF x 0 t 0 t 0 t 0 t 0 t A. B. C. D. E.

8 Consider the following vectors in the x-y plane: A = 5.0 m/s at 45 degrees (1 st quadrant) and B with x component -2.5 m/s and y component -4.5 m/s. a) Add the two vectors and determine the resultant. b) Find the cross product. c) Find the angle between them.

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10 Find final v if starting from rest?

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12 A golf ball is hit from the ground with speed v. In order that it will travel a distance d (in absence of air friction), find the launch angle θ. From the top of a building of height h, Zelda drops a projectile at time t = s later her friend Zeke drops a similar projectile from a window at a height of exactly h/2. The projectiles hit each other at the instant they reach the bottom of the building. Find the time for Zelda s projectile to fall, and the height of the building.

13 Formula sheet (exam 1):

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16 Q2.11 A glider is on an inclined, frictionless track. The x-axis points downhill. At t = 0 the glider is at x = 0 and moving uphill. After reaching the high point of its motion, it moves downhill and returns to x = 0. High point of motion Glider at t = 0 x = 0 Which of the following v x t graphs (graphs of velocity vs. time) best matches the motion of the glider? x v x v x v x v x v x 0 t 0 t 0 t 0 t 0 t A. B. C. D. E.

17 A2.11 A glider is on an inclined, frictionless track. The x-axis points downhill. At t = 0 the glider is at x = 0 and moving uphill. After reaching the high point of its motion, it moves downhill and returns to x = 0. High point of motion Glider at t = 0 x = 0 Which of the following v x t graphs (graphs of velocity vs. time) best matches the motion of the glider? x v x v x v x v x v x 0 t 0 t 0 t 0 t 0 t A. B. C. D. E.

18 In a river 100 m wide, the current flows due south at 2.0 m/s. A boat starts on the east bank with steady speed of 5.0 m/s relative to the water, and a bearing due northwest. a) How long will the boat take to cross the river? b) What is the speed of the boat relative to the bank? c) What is the net acceleration of the boat while crossing, including the influence of the water?

19 Consider the following vectors applied to a small satellite tethered to a space station far from Earth: A = (1.0 N, 2.0 N, 5.0 N); B = (-4.0 N, 0. N, 7.0 N) a) Find a force vector added to these two that would allow the satellite to sit at equilibrium. b) Find the angle between the two vectors.

20 Starting from rest, a Team USA hockey player begins to accelerate at time t = 0 with x, y components (5.0 m/s 2, 3.0 m/s 2 ). Find the hockey player s velocity at the moment when the y-component of her displacement is equal to 10.0 m. If her mass is 80 kg, determine the added force that an opponent pulling backward on her must exert, directed in the x-direction, to reduced her acceleration magnitude to 5.1 m/s 2.

21 Q3.3 The motion diagram shows an object moving along a curved path at constant speed. At which of the points A, C, and E does the object have zero acceleration? A. point A only B. point C only C. point E only D. points A and C only E. points A, C, and E

22 A3.3 The motion diagram shows an object moving along a curved path at constant speed. At which of the points A, C, and E does the object have zero acceleration? A. point A only B. point C only C. point E only D. points A and C only E. points A, C, and E

23 Q3.8 The velocity and acceleration of an object at a certain instant are ( 2 v = 2.0 m/s ) iˆ + ( 3.0 m/s) ˆj 2 ˆ 2 a = 0.5 m/s i 0.2 m/s ˆj ( ) ( ) At this instant, the object is A. speeding up and following a curved path. B. speeding up and moving in a straight line. C. slowing down and following a curved path. D. slowing down and moving in a straight line. E. none of these is correct

24 A3.8 The velocity and acceleration of an object at a certain instant are ( 2 v = 2.0 m/s ) iˆ + ( 3.0 m/s) ˆj 2 ˆ 2 a = 0.5 m/s i 0.2 m/s ˆj ( ) ( ) At this instant, the object is A. speeding up and following a curved path. B. speeding up and moving in a straight line. C. slowing down and following a curved path. D. slowing down and moving in a straight line. E. none of these is correct