(14 pts) 1. A ball is thrown straight up from the ground.
a) What must be the magnitude of its initial velocity if it is to rise to a height of 20.0 m above the point from which it was thrown?
Ans. __19.8 m/s___
b) If the ball has the initial velocity calculated in part (a), what is its total time the air, the total time it takes to travel up and return to its starting point?
Ans. ___4.04 s___
(21 pts) 2. A rock is thrown with a velocity of magnitude 15 m/s and at an angle of 37° above the horizontal from the roof of a building. The horizontal distance from the base of the building to the point where the rock strikes the ground is 60 m.
a) How long is the rock in the air, the time from when it is thrown until it strikes the ground?
Ans. ___5.0 s___
b) What is the height of the building?
Ans. ___77.5 m____
c) What is the magnitude of the velocity of the rock just before it strikes the ground?
Ans.___41.8 m/s___
(18 pts) 3. A river is 900 m wide and the current in the river has a speed of 2.0 m/s due east. A swimmer swims with a speed of 5.0 m/s relative to the water. If the swimmer travels directly north from point A to point B on the opposite bank,
a) How long does it take him to travel from point A to point B?
Ans. ___197 s___
b) In what direction should he head. That is, what is the direction of his velocity relative to the water. Give your answer as an angle with respect to the N,S,E,W compass directions.
Ans.___23.6° W of N___
(21 pts) 4. A box with mass 90 kg is pulled down a ramp by means of a rope that is parallel to the surface of a ramp. The coefficient of kinetic friction between the box and the ramp is 0.90 and the box has an acceleration of a = 0.600 m/s2. The ramp has a slope angle of 37°.
a) What is the magnitude of the normal force exerted by the ramp on the box?
Ans.___704 N___
b) What is the magnitude of the friction force exerted by the ramp on the box?
Ans. ___634 N___
c) What is the tension T in the rope?
Ans. ___157 N___
(26 pts) 5. In the sketch block A has a mass of 4.00 kg and block B has a mass of 20.0 kg. The coefficient of kinetic friction between block B and the horizontal surface is 0.10. Block B is moving to the right with an acceleration of 2.00 m/s2?
a) While the blocks are moving, what is the tension TAB in the rope connecting blocks A and B?
Ans.___47.2 N___
b) While the blocks are moving, what is the tension TBC in the rope connecting blocks B and C?
Ans.__107 N___
c) What is the mass of block C.
Ans.___13.7 kg___