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I)Lecture Multiple Choice (11 questions, 5 points each)

1) /
The vector in the figure that could represent the vector is
A) B) C) D) E) E

Using the following diagram for the next two questions. An object, located at the origin when t=0, moves along the x axis as shown in the diagram.

2) / At which point is the object farthest from its starting point?
A) A B) B C) C D) D E) E
3) / At which point or points is the magnitude of its velocity a minimum?
A) / A and E / D) / E only
B) / D only / E) / B, D, and E
C) / C only
4) / A bolt comes loose from underneath an elevator that is 30 m above the bottom of the elevator shaft. If the bolt reaches the bottom of the elevator shaft in 3.3 s, how fast was the elevator moving when the bolt came loose? Take the positive direction to be upward.
A) -25.3m/s B) -7.1m/s C) 0.0m/s D) 7.1m/s E) 25.3m/s
5) / A river is 0.76 km wide. The banks are straight and parallel. The current is 5.0 km/h and is parallel to the banks. A boat has a maximum speed of 3 km/h in still water. The pilot of the boat wishes to travel on a straight line from A to B, where AB is perpendicular to the banks. The pilot should
A) / head directly across the river.
B) / head 68º upstream from the line AB.
C) / head 22º upstream from the line AB.
D) / give up. The trip from A to B is not possible with this boat.
E) / head 37º upstream from the line AB.
6) / You shoot an arrow in a high arc toward a target located some distance away. At the highest point in its flight, the arrow's
A) / velocity and acceleration are both nonzero.
B) / velocity is zero but its acceleration is nonzero.
C) / velocity is nonzero but its acceleration is zero.
D) / velocity and acceleration are both zero.
E) / Insufficient information is given to answer correctly.
7) / The initial position and velocity of a projectile are given by and respectively, and where r is in m and v in m/s. The position in the horizontal direction (in m) as a function of time is
A) / x(t) = 6t
B) / x(t) = 3 + 6t
C) / x(t) = 3 + 6t + gt2
D) / x(t) = 4 + 8t
E) / x(t) = 4 + 8t + gt2
8) / A merry-go-round completes one revolution in 40 s. What is the centripetal acceleration of a rider located at a distance 2 m from the center of the merry go-round?
A) / m/s2 / D) / /100 m/s2
B) /  m/s2 / E) / 2 m/s2
C) /  m/s2
9) / A force accelerates a body of mass M. The same force applied to a second body produces three times the acceleration. What is the mass of the second body?
A) M B) 3M C) M/3 D) 9M E) M/9
10) / Rachel has been reading her physics book. She takes her weighing scales into an elevator and stands on them. If her weight is 690 N, and the elevator moves upward at 0.25g and then down at 0.25g, what is the difference between the up and down scale readings?
A) 690 N B) 520 N C) 170 N D) 345 N E) 1.04  103 N
11) / Two masses m1 = 12 kg and m2 = 35 kg are held connected by a massless rope hung over a frictionless light pulley. If the masses are released then the magnitude of the tension in the string is /
A) 118 N B) 343 N C) 461 N D) 265 N E) 175 N

II)Lecture Question (25 points)

As shown in the diagram on the right, a 1.5-kg block is prevented from sliding down a frictionless incline by a string attached to the left wall. The string is parallel to the incline and the incline has a slope of 30 degrees with respect to horizontal. /
1)(7 points) Draw a free-body diagram of the block in the box to the right. Label all the forces, and clearly define any symbol you use. /

2)(5 points) What is the magnitude of the tension in the rope?

Someone cuts the rope and the block accelerates down the incline at 4.9 m/s2. Just before the block goes off the cliff the magnitude of the blocks velocity is 10.0 m/s.

3)(6 points) How far did the block slide down the incline, i.e. what is D?

4)(7 points) The block takes 0.75 s to hit the ground. How high is the cliff, i.e. what is H?

Phys 121 BMidterm Exam 1 – Version APage 1