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Force and acceleration

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11. What is the weight of a 2.50-kg bag of sand on the surface of the earth?
12. A 2.00-kg projectile is fired at an angle of 20.0 degrees. What is the magnitude of the force exerted on the projectile when it is at the highest position of its trajectory?
13. A 44-kg child steps onto a scale and the scale reads 430 N. What is the magnitude of the normal force acting on the child?
14. The wheels of an automobile are locked as it slides to a stop from an initial speed of 30.0 m/s. If the coefficient of kinetic friction is 0.200 and the road is horizontal, approximately how long does it take the car to stop?
Two blocks rest on a horizontal frictionless surface as shown. The surface between the top and bottom blocks is roughened so that there is no slipping between the two blocks. A 30- N force is applied to the bottom block as suggested in the figure.
15. What is the acceleration of the two block system?
16. What is the force of static friction between the top and bottom blocks?
17. What is the minimum coefficient of static friction necessary to keep the top block from slipping on the bottom block?

18. A boy pulls a sled of mass 5.0 kg with a rope that makes a 60.0 angle with respect to the horizontal surface of a frozen pond. The boy pulls on the rope with a force of 10.0 N; and the sled moves with constant velocity. What is the coefficient of friction between the sled and the ice?
19. A rock is suspended from a string, and it accelerates downward. Which one of the following statements concerning the tension in the string is true?

20. What is the tension in the right-hand cable?
21. What is the tension in the horizontal cable?

22. A rope connects boat A and boat B. Boat A starts from rest and accelerates to a speed of 9.5 m/s in a time t = 47 s. The mass of boat B is 540 kg. Assuming a constant frictional force of 230 N acts on boat B, what is the magnitude of the tension in the rope that connects the boats during the time that boat A is accelerating?

23. A 4-kg block and a 2-kg block can move on the horizontal frictionless surface. The blocks are accelerated by a 12-N force that pushes the larger block against the smaller one. Determine the force that the 2-kg block exerts on the 4-kg block.


Solution Preview

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11. W = mg = 2.5 * 9.8 = 24.5 N
Answer: C

12. The only force on the projectile is the gravitational force mg = 2.00 * 9.8 = 19.6 N
Answer: A

13. The reading of the scale is due to the force of the child onto the scale. By Newton's 3rd law, the supporting force or the normal force acting on the child is equal to the force on the scale by the child. So the normal force is 430 ...

Solution Summary

Force and acceleration are investigated. The solution is detailed and well presented.