What did I do wrong in these PCS211 questions about Work and Energy? Please take your time to correct it!

2. [0/2 Points] DETAILS PREVIOUS ANSWERS SERPSE10 7.2.P.003. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A man pulled a 22.0 kg object 10.6 cm vertically with his teeth. (a) How much work (in ]) was done on the object by the man in this lift, assuming the object was lifted at constant velocity? (Include the sign of the value in your answer.) -22.85 X You are looking for the work done on the object. Will the work be negative or positive? ] (b) What total force (in N) was exerted on the man's teeth during the lift? (Enter the magnitude.) 0 X The sum of the forces is zero, because the acceleration is zero. You are looking for the force exerted on the man's teeth, which is not zero. According to Newton's third law, the upward force must be equal in magnitude to the downward force, which is the gravitational force in this case. N Need Help? Read It4. [0/1 Points] DETAILS PREVIOUS ANSWERS SERPSE10 7.2.P.004.MI. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Spiderman, whose mass is 70.0 kg, is dangling on the free end of a 12.8-m-long rope, the other end of which is fixed to a tree limb above. By repeatedly bending at the waist, he is able to get the rope in motion, eventually getting it to swing enough that he can reach a ledge when the rope makes a 0 = 58.60 angle with the vertical. How much work was done by the gravitational force on Spiderman in this maneuver? 4.575 X The response you submitted has the wrong sign. kJ Need Help? Read It Master It 5. [0/1 Points] DETAILS PREVIOUS ANSWERS SERPSE10 7.3.P.006. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Two vectors, A and B, have magnitudes of 4.95 units and 8.73 units, respectively. The angle between A and B is 49.50. What is A . B? A . B = 97 X Use A . B = ABcos(0). Need Help? Read It 6. [0/1 Points] DETAILS PREVIOUS ANSWERS SERPSE10 7.3.OP.005. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER For A= 51 + j - 4k, B = -31 + j + 5k, and C = 5j - 5k, find C . (A - B). +14 X Be careful when subtracting vectors that have negative values for their components; it is easy to get the signs wrong. Need Help? Read It Watch It12. [1/3 Points] DETAILS PREVIOUS ANSWERS SERPSE1O 7.5.P.021. MY NOTES l | ASK YOUR TEACHER I | PRACTICE ANOTHER A OJDUrkg particle has a speed of 100 m/s at point and kinetic energy of 7.90 J at point . (a) What is its kinetic energy at @? W (In) What is Its speed at @? E m (c) What is the net work done on the particle by external furces as It moves frurn to @? x The work done by the net force is equal to the change In kinetic energy. 15 this given by the final minus the Initial kinetic energy or the Initial minus the final kinetic energy? J 14. [3/4 Points] DETAILS PREVIOUS ANSWERS SERPSE10 7.5.P.027. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A 6.02-kg object passes through the origin at time t = 0 such that its x component of velocity is 4.60 m/s and its y component of velocity is -2.79 m/s. (a) What is the kinetic energy of the object at this time? 67.121 X Your response differs from the correct answer by more than 10%. Double check your calculations. J (b) At a later time t = 2.00 s, the particle is located at x = 8.50 m and y = 5.00 m. What constant force acted on the object during this time interval? magnitude 31.91 N direction 93.79 measured from the +x axis (c) What is the speed of the particle at t = 2.00 s? 8.711 m/s20. [0/1 Points] DETAILS PREVIOUS ANSWERS SERPSE10 7.A.OP.030. MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER A person throws a 0.150 kg ball with a speed of 43.2 m/s at an angle of 28.0 to the horizontal. Calculate the kinetic energy (in ]) of the ball at its highest point in the trajectory. 20.98 X Remember that for a projectile, the horizontal component of velocity is constant. At the apex, the ball's velocity is purely horizontal. Use this velocity to determine the kinetic energy. J Need Help? Read It