# Science Mining I

Topics: Friction, Force, Acceleration Pages: 13 (3758 words) Published: February 18, 2013
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For any other study information see the brochure my Studies@Unisa. 9

SMI181Q/101/2013

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CONCLUSION
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ADDENDUM A: COMPULSORY ASSIGNMENTS FOR FIRST SEMESTER SEMESTER 1 Assignment 1 Due date: 08 March 2013 Assignment Unique number: 748509 (Students registered for the first semester only) Instruction In preparing for this assignment do not rely only on the study guide. This assignment consists of twenty (20) questions. 1. A 2.5-m ladder leans against a wall and makes an angle with the wall of 32° as shown in the figure. What is the height (h) above the floor where the ladder makes contact with the wall? [5]

1) 2) 3) 4) 5)

2.1 m 1.3 m 2.4 m 1.6 m 1.9 m

2. Carl Lewis set a world record for the 100.0-m run with a time of 9.86 s. If, after reaching the finish line, Mr. Lewis walked directly back to his starting point in 90.9 s, what is the magnitude of his average velocity for the 200.0 m? [5] 1) 2) 3) 4) 5) 10 1.10 m/s 1.98 m/s 5.60 m/s 10.1 m/s zero

SMI181Q/101/3/2013 3. A car is moving at a constant velocity when it is involved in a collision. The car comes to rest after 0.450 s with an average acceleration of 65.0 m/s2 in the direction opposite that of the car's velocity. What was the speed, in km/h, of the car before the collision? [5] 1) 2) 3) 3) 5) 29.2 km/h 144 km/h 44.8 km/h 80.5 km/h 105 km/h

4. A car accelerates from rest at point A with constant acceleration of magnitude a and subsequently passes points B and C as shown in the figure.

The distance between points B and C is x, and the time required for the car to travel from B to C is t. Which expression determines the average speed of the car between the points B and C? [5] 1) 2) 3) 4) 5) v2 2ax

v
v

x t
xt

v
v

1 2 at 2
at

5. An elevator is moving upward with a speed of 11 m/s. Three seconds later, the elevator is still moving upward, but it's speed has been reduced to 5.0 m/s. What is the average acceleration of the elevator during the 3.0 s interval? [5] 1) 2) 3) 4) 5) 2.0 m/s2, downward 2.0 m/s2, upward 5.3 m/s2, downward 5.3 m/s2, upward 2.7 m/s2, downward

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SMI181Q/101/2013 6. A 2.0-N rock slides on a frictionless inclined plane. Which one of the following statements is true concerning the normal force that the plane exerts on the rock? [5]

1) The normal force is zero. 2) The normal force is 2.0 N. 3) The normal force is greater than 2.0 N. 4) It increases as the angle of inclination, q , is increased. 5) The normal force is less than 2.0 N, but greater than zero.

7. A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure.

Complete the following statement: If the 4-kg block is to begin sliding, the coefficient of static friction between the 4-kg block and the surface must be: [5] 1) less than zero. 2) greater than 2. 3) greater than 1, but less than 2. 4) greater than 0.5, but less than 1. 5) less than 0.5, but greater than zero.

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SMI181Q/101/3/2013 8. Two sleds are hooked together in tandem as shown in the figure. The front sled is twice as massive as the rear sled.

The sleds are pulled along a frictionless surface by an applied force F. The tension in the rope between the sleds is T. Determine the ratio of the magnitudes of the two forces, T/F. [5] 1) 0.25 2) 0.33 3) 0.50 4) 0.67 5) 2.0 9. A constant force of 25 N is applied as shown to a block which undergoes a displacement of 7.5 m to the right along a frictionless surface while the force acts. What is the work done by the force? [5]

1) zero 2) +94 J 3) -94 J 4) +160 J 5) -160 J

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10.

SMI181Q/101/2013 A roller-coaster car is moving at 20 m/s along a straight horizontal track. What will its speed be after climbing the 15-m hill shown in the figure if friction is ignored? [5]

1) 17 m/s 2) 7 m/s 3) 5 m/s 4) 10 m/s 5) 14 m/s 11. A 100-kg cannon at rest contains a 10-kg cannon...