- #1

r3dxP

As a consequence, the object

A. stops abruptly

B. stops during a short time interval

C. changes direction

D. continues at a constant velocity

E. change velocity in an unknown manner

i got C.

2. A bullet of mass 1.8 X 10-3 kg, moving at 500 m/s impacts a large fixed block of wood and travels 6 cm before coming to rest. Assuming that the acceleration of the bullet is constant, find the force exerted by the wood on the bullet

do not know

3. A traffic light is supported by 2 wires as shown below. Is the tension in the wire that is more nearly vertical greater or less than the tension in the other wire?

T1 = T2 tan 30degrees

T1 = .6T2

the wire that is more vertical(T2) has a greater thension than that of the other wire (T1)

4. Your car is stuck in a mud hole. You are alone, but you have a long, strong rope. Having studied physics, you tie the rope tautly to a telephone pole and pull on it sideways as shown below.

A. Find the force exerted by the rope on the car when the angle is 3o and you are pulling with a force of 400 N but the car does not move.

2Tsin3degrees=400N == T=3820N ~= 4000N

B. How strong must the rope be if it takes a force of 600 N to move the car when is 4o? (I know I am not much of an artist!)

2Tsin4degrees=600N == T=4301N ~= 4000N

5. A 65-kg student weighs himself on a scale mounted on a skateboard that is rolling down an incline as shown below. Assume there is no friction so that the force exerted by the incline on the skateboard is normal to the incline. What is the reading on the scale if = 30degrees?

N = mgcos30degrees where m=65kg and g=9.8m/s^2; F=552N

6. Five forces pull on the 4.0 kg box as shown below. Find the boxs acceleration as a magnitude and direction.

y forces: 5N+14sin30degrees - 17N = ma

x forces: 3N + 14cos30degrees - 11N = ma

umm from here, i didnt know what to do.. my attempt was :

sin90/6.5 = sin x/4.1 x=39.1degrees; 6.5N/4.0kg = 1.6m/s^2; due 39.1+270=309.1degrees due east.

from 7-12, i do not know how to do any of these. any help will be appreciated.

7. A block with mass m is supported by a cord C from the ceiling, and a similar cord D is attached to the bottom of the block. (See below) Explain this: If you give a sudden jerk to D, it will break, but if you pull on D steadily, C will break.

8. In a laboratory experiment, an initially stationary electron (mass = 9.11 X 10-31 kg) undergoes a constant acceleration through 1.5 cm, reaching a speed of 6.0 X 106 m/s at the end of that distance.

A. What is the magnitude of the force accelerating the electron?

B. What is the weight of the electron?

9. A golfer chips a ball toward a vertical wall 20.0 m straight ahead, trying to hit a 30.0 cm diameter red circle painted on the wall. The target is centered about a point 1.20 m above the point where the wall intersects the horizontal ground. On one try, the ball leaves the ground with a speed of 15.0 m/s and at an angle of 35.0o above the horizontal ground and then hits the wall on a vertical line through the circles center.

A. How long does the ball take to reach the wall?

B. Does the ball hit the red circle (give the distance to the circles center)?

C. What is the speed of the ball just before it hits?

D. Has the ball passed the highest point of its trajectory when it hits?

10. A baseball is hit at Fenway Park in Boston at a point 0.762 m above home plate with an initial velocity of 33.53 m/s directed 55.0o above the horizontal. The ball is observed to clear the 11.28 m high wall in left field (the Green Monster!) 5.00 s after it is hit, at a point just inside the left-field foul line pole. Find

A. the horizontal distance down the left field foul line from home plate to the wall

B. the vertical distance by which the ball clears the wall

C. the horizontal and vertical displacements of the ball with respect to home plate 0.500 s before it clears the wall.

11. In the figure below, a ball is fired at an angle of 30.0o from the horizontal, landing 3.00 s later after traveling a horizontal distance of 100 m.

A. At what height h above the firing level does the ball land?

B. At what speed is it fired?

C. At what speed does it land?

12. You are to throw a ball with a speed of 12.0 m/s at a target that is 5.00 m above the level at which you release the ball (see below). You want the balls velocity to be horizontal at the instant it reaches the target.

A. At what angle from the horizontal must you thrown the ball?

B. What is the horizontal distance from the release point to the target?

C. What is the speed of the ball just as it reaches the target?