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The following physics responses are provided by a student and, as such, should be considered in that context. While every effort is made for accuracy, absolute correctness cannot be fully guaranteed.
| C | I | Question | Answer |
|---|---|---|---|
| 11 | A waterfall is 145 m high. What is the increase in water temperature at the bottom of the falls if all the initial potential energy goes into heating the water? (g = 9.8 m/s^2 , cw = 4186 J/kg×°C) | 0.34°C | |
| 4 | Dana uses a rope to pull a box that weighs 300 N across a level surface with constant velocity. The rope makes an angle of 30° above the horizontal and the tension in the rope is 100 N. What is the coefficient of friction? | 0.35 | |
| 10 | A brass cube, 10 cm on a side, is raised in temperature by 200°C. The coefficient of volume expansion of brass is 57*10^-6/C°. By what percentage is any one of the 10-cm edges increased in length? | 0.38% | |
| 4 | A 300-kg crate is placed on an adjustable inclined plane. As one end of the incline is raised, the crate begins to move downward. If the crate slides down the plane with an acceleration of 0.70 m/s2 when the incline angle is 25°, what is the coefficient of kinetic friction between ramp and crate? (g = 9.8 m/s2) | 0.39 | |
| 8 | An ice skater spins at 2.5 rev/s when his arms are extended. He draws his arms in and spins at 6.0 rev/s. By what factor does his moment of inertia change in the process? | 0.42 | |
| 3 | A ball is rolled horizontally off a table with an initial speed of 0.24 m/s. A stopwatch measures the ball's trajectory time from table to the floor to be 0.30 s. What is the height of the table? (g = 9.8 m/s2 and air resistance is negligible) | 0.44m | |
| 13 | A 0.20-kg block rests on a frictionless level surface and is attached to a horizontally aligned spring with a spring constant of 40 N/m. The block is initially displaced 4.0 cm from the equilibrium point and then released to set up a simple harmonic motion. A frictional force of 0.3 N exists between the block and surface. What is the speed of the block when it passes through the equilibrium point after being released from the 4.0-cm displacement point? | 0.45 m/s | |
| 7 | A 0.15-m-radius grinding wheel starts at rest and develops an angular speed of 12.0 rad/s in 4.0 s. What is the average tangential acceleration of a point on the wheel's edge? | 0.45 m/s^2 | |
| 2 | A bird, accelerating from rest at a constant rate, experiences a displacement of 28 m in 11 s. What is its acceleration? | 0.46 m/s^2 | |
| 7 | A fan blade, initially at rest, rotates with a constant acceleration of 0.025 rad/s2. What is its angular speed at the instant it goes through an angular displacement of 4.2 rad? | 0.46 rad/s | |
| 4 | A 200-N crate rests on an ramp; the maximum angle just before it slips is 25° with the horizontal. What is the coefficient of static friction between crate and ramp surfaces? | 0.47 | |
| 7 | A bucket in an old well is hoisted upward by a rope which winds up on a cylinder having a radius of 0.050 m. How many rev/s must the cylinder turn if the bucket is raised at a speed of 0.15 m/s? | 0.48 rev/s | |
| 8 | An object with mass m and moment of inertia I is spinning with an angular momentum L. Its kinetic energy is: | 0.5 L^/I. | |
| 9 | A uniform pressure of 7.0*10^5 N/m^2 is applied to all six sides of a copper cube. What is the percentage change in volume of the cube? (for copper, B = 14*10^10 N/m^2) | 0.5*10^-3 % | |
| 2 | An object moves 20 m east in 30 s and then returns to its starting point taking an additional 50 s. If west is chosen as the positive direction, what is the average speed of the object? | 0.50 m/s |