La tarea de física

PROBLEMS

EFFECTS OF MOTION

1. A tennis player accelerates the tennis ball with a mass of 75 grams, from rest to a speed of 45 m/s, if the acceleration is constant when the racket hits the ball at a distance of O. 85 meters, what is the force magnitude exerted on the ball by the racket?

3. A jet plane with a weight of2.75 x 106N is ready for taking off. If its engines give a push Of 6.35 x 106 N, what distance will it need to have a minimum speed for taking off of 285 km/h?

5. An automobile with mass2300 kg starts from rest to obtain a speed of 72 km/h in 10 seconds. Find the magnitude of the exerted force.

HORIZONTAL AND FRICTIONLESS INCLINED PLANE MOTION

7.A force of 400 N is exerted on an object with mass 30 kg to slide up on a 450 slope (figure 1.70). If the force is parallel to the plane and friction less, calculate the object's acceleration and the normal force.

9. A force of 150 N is exerted on a 100-N object makes an angle of 300º above the horizontal. If the object slides on a horizontal frictionless surface, calculate the acceleration and normal force.

11. A force of 160 N is exerted on 20-N object. The object is pushed upwards by a slope with an angle of 3C above the horizontal. If the force is parallel to the plane and frictionless, calculate the object's acceleration and the normal force.

ILL. MOTION ON HORIZONTAL AND INCLINED PLANE

13. A force of 35 N is exerted on an object to slide it with constant speed on a horizontal surface (figure 1.72). If the object with mass12 kg, what is the coefficient of kinetic friction between the object and the surface?

15. A 300 N force, parallel to an inclined plane at 400, pushes upwards a box with mass 25 kg and produces an acceleration of 1.5 m/s^2 (Figure '1.74). Calculate the coefficient of kinetic frictionμk between the box and the inclined plane.

17. A wooden box with mass 30 kg is pushed along horizontal surface by a parallel force of 135 N. If the box slides with constant speed, determine the coefficient of kinetic friction between box and surface.

19. A skier with mass 80 kg slides on a hill with a slope of 370. If the coefficient of kinetic friction is 0.12, calculate the acceleration of skier.

STATIC

21.An object with mass 14 kg suspended from a chord T1 pulled horizontally by a chord T2 and fasten to the chord T1 makes an angle of 500 with the wall. (See figure 1.77). Determine tension T1 and T2.

23. At a twin's boys party a piñata with weight 30 N is suspended from a rope that makes an angle 300 above the horizontal, as it is shown on figure 1.79. Calculate the exerted force by each child.

CONCEPT ANALYSIS

ANSWER THE FOLLOWING QUESTIONS AND EXPLAIN YOUR ANSWERS

VECTORS

1. Mention the difference between scalar and vector quantities.

2. How does the magnitude of the resultant vary between two vectors if the angle between them decreases?

3. What is the addition of three vectors that make a closed triangle?

4. What is the graphical procedure to add two concurrent vectors?

5. What is the graphical procedure to add two non-concurrent vectors?

6. Two vectors of force have magnitude of F1 8 N and F2 10 N, what is the angle for the magnitude of the resultant is maximum? And minimum?

7. Determine the magnitudes of the maximum and minimum resultant of the previous question.

8. What are the conditions where the magnitude of a vector is equal to one of its components?

9. If a vector F is sketched on a plane xy, what interval of values can take the angle if:

a. Its components x and y are positive

b. Its component x is positive and its component y is negative

c. Its components x and y are negative

d. Its component x is negative and its component y is positive

DYNAMICS

10. A resultant force F produces an acceleration a on a car. If now the resultant force is duplicated 2F, what will be the change in the acceleration of the car?

11. A resultant force F produces an acceleration a on a truck. If now it is load in such a way that double the mass. What will be the change in the acceleration of the truck?

12. A truck can accelerate 3m/s , if it loses part of its load, its mass is 1/3 of its initial mass m, what acceleration can develop the truck if the force does not change?

13. What do we impulse walk?

14. If a cannon fires a shell, how do you compare the magnitude of the force that the cannon exerts on the shell with the force that the shell exerts on the cannon? How are the cannon and the shell accelerations?

15. Suppose that you weigh in front of a sink. Using the idea of action and reaction, why is lower the weighing scale reading when you push downwards the sink? Why is it greater weighing scale reading when you pull upwards the sink from the bottom?

16. If two 40 N weights are hanged on each end of the dynamometer which is placed horizontally on the table. Will the dynamometer show a reading of 40 N or 80 N? Justify your answer.

17. Your weight change when you travel in an elevator that moves at constant speed? If the elevator accelerates, will your weight change?

18. A body on the Earth has mass of 30 Kg, What will be the mass of the body if it is taken to Saturn where the gravity is 14m/s?

19. If a truck accelerates

...