Physics 201 MWF10:20 Fall 2000 (Ford)

Exam I Chapts 1--4 Cutnell and Johnson 4th ed


Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.


(18 pts) 1. An oceanliner is heading due north with a speed of 6.0 m/s relative to the water. A sailboat is traveling due east relative to the water. The speed of the sailboat relative to a passenger standing on the deck of the oceanliner is 9.0 m/s.

a) What is the magnitude of the velocity of the sailboat relative to the water?

Ans. ___ 6.71 m/s____

b) What is the direction of the velocity of the sailboat relative to the passenger on the oceanliner? Show the direction of this velocity in a clearly labeled diagram.

Ans.__ 41.8° S of E_____


(20 pts) 2. Just as you enter the freeway in your car a truck traveling at a constant speed of 40 m/s is alongside you. At this instant your car has a speed of 20 m/s. Your car maintains a constant acceleration of 0.5 m/s² and the truck continues at constant velocity as both vehicles travel along a straight stretch of road.

a) How much time elapses until your car catches up with the truck?

Ans.____ 80 s___

b) How far do you travel before you catch up with the truck?

Ans.___ 3200 m___

c) What is the magnitude of your velocity when you catch up with the truck?

Ans.___ 60 m/s___


(22 pts) 3. A rock is thrown on level ground with speed 20 m/s and in a direction of 37° above the horizontal. The rock strikes a building that is a horizontal distance of 30 m from the point where the rock was thrown.

a) How much time elapses from when the rock was thrown until it hits the building?

Ans.___ 1.88 m____

b) How high above the ground is the point where the rock strikes the building?

Ans.___ 5.3 m____

c) What are the magnitude and direction of the velocity of the rock just before it strikes the building?

Ans. magnitude ___ 17.2 m/s___

direction __ 21.8° below horizontal____


(18 pts) 4. A block with mass 20 kg is suspended from a rope. The other end of the rope is connected to a block of mass m that sits on a table. The rope and the frictionless pulley have negligible mass and there is no friction between the table and the block that sits on it. The system is released from rest, the hanging block descends, and while the blocks are moving the tension in the rope is observed to be 80 N.

a) What is the magnitude of the acceleration of the 20 kg block?

Ans ____5.8 m/s²____

b) What is the mass m of the block that is on the table?

Ans. ___13.8 kg___


(22 pts) 5. A 20-kg block sits on an incline that slopes upward at an angle of 37° above the horizontal. The coefficient of kinetic friction between the block and the incline is 0.40. A force T that is parallel to the surface of the incline and directed up the incline is applied to the block and it is observed that the block moves up the incline with an acceleration of 3.0 m/s².

a) What is the magnitude of the friction force that the incline exerts on the block while the block is moving?

Ans. ___62.6 N___

b) What is the magnitude of the force T?

Ans.___241 N___