PH 211 Recitation
Homework Spring 2008
Chapter 02 (due third week of term)
Two cars move in opposite directions toward each other on a level, straight, one-lane road. When both drivers begin to brake, their front bumpers are 275 meters apart. The smaller car is initially moving at 25.0 m/s and the larger is initially moving at 30.0 m/s. The magnitude of the acceleration of the smaller car is 20.0% greater than the magnitude of the acceleration of the larger. Determine the magnitude of acceleration for each car such that when their front bumpers touch, they have just come to rest.
Chapter 03 (due fourth week of term)
The sum of three vectors is zero. The magnitude of the first vector is twice the magnitude of the second. The first and second vectors are perpendicular. The direction of the third vector is along the negative x-axis. What are the directions of the other two vectors? There are two possible sets of answers. For both sets of answers, give the directions in standard polar form.
Chapter 04 (due fifth week of term)
A projectile is launched up and to the right at an angle θ above the horizontal from (x, y) = (0, h) with an initial speed v0. (a) What is its maximum vertical position? (b) How much time does it take for the projectile to reach the x-axis after being launched? Give both answers in terms of h, θ, v0, and/or g. For full credit, express your answers using one simple fraction that has been factored completely.
Chapter 05 (due sixth week of term)
A 135-kg crate is lowered at constant velocity with a rope down a frictionless ramp inclined at an angle of 30.0 degrees with the horizontal. The rope is parallel to the ramp. What are the magnitudes and directions of all of the forces acting on the crate?
Chapter 06 (due seventh week of term)
A worker pushes with force F directly along the handle of a mop down and to the right at an angle θ below the horizontal. The head of the mop moves to the right along the floor. The static and kinetic coefficients between the mop head and the floor are µs and µk respectively. The mass of the mop head is m. Ignore the mass of the handle. (a) If the mop head moves with constant velocity, then what is F in terms of θ, µs, µs, m, and/or g? (b) Find the maximum angle θmax such that the mop head still moves in terms of F, µs, µs, m, and/or g.
Chapter 07 (due eighth week of term)
Three rectangular blocks of equal mass m slide to the right along a frictionless horizontal surface accelerated by a force F applied to the left side of the left-most block. (a) Draw a free-body diagram for each block. (b) Determine the magnitudes and directions of all of the forces on each block in terms of m, F and/or g.
Chapter 09 (due ninth week of term)
Two objects moving perpendicularly collide and stick together. The mass of the first object is three times bigger than the mass of the second. Before they collide, the speed of the second object is 5.00 m/s and the speed of the first is 1.00 m/s. What is the speed of the two objects after they collide?
Chapter 10 (due tenth week of term)
A small object begins at the top of a frictionless solid sphere. Its initial speed is negligibly small. The sphere is stationary at all times. The small object then slides down the surface of the sphere. At one point the small object loses contact with the sphere. Draw a line from this point to the center of the sphere. What is the angle between this line and the horizontal?