practice exam 2.pdf

PH 1110 Name (Print) : Examination 2 Newton’s Second Law: 𝐹⃗𝑛𝑒𝑡 = ∑ ⃗⃗⃗ 𝐹𝑖 = 𝑚𝑎⃗ g = 9.80 m/s2 Force of friction Ff =  N, where N is the normal force....

PH 1110 Name (Print) : Examination 2 Newton’s Second Law: 𝐹⃗𝑛𝑒𝑡 = ∑ ⃗⃗⃗ 𝐹𝑖 = 𝑚𝑎⃗ g = 9.80 m/s2 Force of friction Ff =  N, where N is the normal force. 𝑣2 The magnitude of the radial acceleration : 𝑎𝑟 = 𝑅 The work done by a constant force F: 𝑊𝐹 = 𝐹𝑑 cos 𝜃 The work done by a conservative force : 𝑊𝑐𝑜𝑛 = −∆𝑈 = 𝑈𝑖 − 𝑈𝑓 The Work-Energy Theorem: 1 1 Wtotal = K final − Kinitial = mv 2f − mvi2 2 2 The conservation of energy: 1 1 1 1 𝑚𝑣𝑖2 + 𝑘𝑥𝑖2 + 𝑚𝑔𝑦𝑖 + 𝑊𝑂𝑡ℎ𝑒𝑟 = 𝑚𝑣𝑓2 + 𝑘𝑥𝑓2 + 𝑚𝑔𝑦𝑓 2 2 2 2 𝑂𝑡ℎ𝑒𝑟 = (𝑁𝑜𝑛𝑐𝑜𝑛𝑠𝑒𝑟𝑣𝑎𝑡𝑖𝑣𝑒 + 𝐸𝑥𝑡𝑒𝑟𝑛𝑎𝑙)𝐹𝑜𝑟𝑐𝑒𝑠 Impulse – Momentum Theorem: 𝐽⃗ = ⃗⃗⃗⃗⃗⃗⃗⃗ 𝐹𝑎𝑣𝑒 ∆𝑡 = 𝑚𝑣 ⃗⃗⃗⃗⃗𝑓 − 𝑚𝑣 ⃗⃗⃗⃗𝑖 Conservation of Linear Momentum m1 v1i + m2 v 2i +... = m1v1 f + m2 v 2 f +...  1) Two objects have masses m and 5m, respectively. They both are placed side by side (i.e., same height) on a frictionless inclined plane and allowed to slide down from rest. o The two objects reach the bottom of the incline at the same time. o It takes the heavier object 10 times longer to reach the bottom of the incline than the lighter object. o It takes the lighter object 10 times longer to reach the bottom of the incline than the heavier object. o It takes the lighter object 5 times longer to reach the bottom of the incline than the heavier object. o It takes the heavier object 5 times longer to reach the bottom of the incline than the lighter object. 2) A small car has a head-on collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct? o The small car experiences the greater average force. o The truck experiences the greater average force. o It is impossible to tell since the masses are not given. o It is impossible to tell since the velocities are not given. o The small car and the truck experience the same average force. 3) Which one of the following statements concerning kinetic energy is true? o Kinetic energy can be measured in watts. o Kinetic energy is always equal to the potential energy. o Kinetic energy is always positive. o Kinetic energy is a quantitative measure of inertia. o Kinetic energy is directly proportional to velocity. 4) Which, if any, of the following statements concerning the work done by a conservative force is NOT true? o It can always be expressed as the difference between the initial and final values of a potential energy function. o When the starting and ending points are the same, the total work is zero. o It is independent of the path of the body and depends only on the starting and ending points. o All of the above statements are true. o None of the above statements are true. 5) In an INELASTIC collision between two objects o the momentum of each object is conserved. o the kinetic energy of each object is conserved. o the kinetic energy of the system is conserved, but the momentum of the system is not conserved. o the momentum of the system is conserved but the kinetic energy of the system is not conserved. o both the momentum and the kinetic energy of the system are conserved. 6) Is it possible for a system to have negative potential energy? o Yes, as long as the total energy is positive. o No, because the kinetic energy of a system must equal its potential energy. o Yes, as long as the kinetic energy is positive. o No, because this would have no physical meaning. o Yes, since the choice of the zero of potential energy is arbitrary. 7) Two objects with masses, m1 and m2, have the same kinetic energy and are both moving to the right. The same constant force F is applied to the left to both masses. If m1 = 3 m2, the ratio of the stopping distance of m1 to that of m2 is: o 1:3 o 3:1 o 6:1 o 1:6 o 1:1 8) A worker lifts a 20.0-kg bucket of concrete from the ground up to the top of a 20.0-m tall building. The bucket is initially at rest, but is traveling at 4.00 m/s when it reaches the top of the building. What is the minimum amount of work that the worker did in lifting the bucket? o 400 J o 160 J o 3.92 kJ o 4.08 kJ o 560 J 9) A 60.0-kg person drops from rest a distance of 1.20 m to a platform of negligible mass supported by an ideal stiff spring of negligible mass. The platform drops 6.00 cm before the person comes to rest. What is the spring constant of the spring? o 2.56 × 105 N/m o 4.12 × 105 N/m o 3.92 × 105 N/m o 8.83 × 104 N/m o 5.45 × 104 N/m 10) [ 4 pts] A student slides her 80.0-kg desk across the level floor of her dormitory room a distance 4.00 m at constant speed. If the coefficient of kinetic friction between the desk and the floor is 0.400, how much work did she do? o 128 J o 1.26 kJ o 24.0 J o 26.7 J o 3.14 kJ 11 In the figure, a 700-kg crate is on a rough surface inclined at 30°. A constant external force P = 5600 N is applied horizontally to the crate. As the force pushes the crate a distance of 3.00 m up the incline, the speed changes from 1.40 m/s to 2.50 m/s. How much work does gravity do on the crate during this process? o -3400 J o -10,300 J o +3400 J o Zero o +10,300 J 12) A 1.2-kg toy-bomb slides on a smooth surface along the x-axis with a speed of 0.50 m/s. At the origin 0, the bomb explodes into two fragments. Fragment 1 has a mass of 0.40 kg and a speed of 0.90 m/s along the negative y-axis. In the figure, the angle θ, made by the velocity vector of fragment 2 and the x-axis, is closest to o 31° o 53° o 38° o 59° o 37° 13) During a collision with a wall, the velocity of a 0.200-kg ball changes from toward the wall to 12.0 m/s away from the wall. If the time the ball was in contact with the wall was 60.0 ms, what was the magnitude of the average force applied to the ball? o 40.0 N o 107 N o 16.7 N o 26.7 N o 13.3 N