Question Four forces (measured in Newtons) act on a crate. The forces are given by the vectors: F₁ = 2121-136ĵ+241k N. F₂ = 108 + 144) + 189k N. F₂ = -400 + 180j + 240k N, and F₂ = -270k N Given: The magnitude of the resultant force = 449.2 N. The work done by the force F, is 770.3J. • The moment of the force F₂ = (-108î - 180k) N/m a) What is the angle (in degrees to 2 decimal places) between the force vectors F₂ and F3? b) What is the force vector, F, that acts in the opposite direction to the force F₂ and has magnitude of 203 Newtons?

Discuss whether any work is being done by each of the following agents and, If so, whether the work is positive or negative. (a) a chicken scratching the ground A chicken does work on the ground. O The ground does work on the chicken. No work is done. Is the work positive or negative? The work is positive. The work is negative. No work Is done. (b) a person studying (holding up a book but not moving it) • The person does work on a book. O The book does work on the person. No work is done. Is the work positive or negative? The work is positive. The work is negative. No work is done. (c) a crane lifting a bucket of concrete The crane does work on the bucket. The bucket does work on the crane. No work is done. Is the work positive or negative? The work is positive. The work is negative. No work is done. (d) the force of gravity on the bucket in part (c) O The bucket does work on gravity. MacBook Air

and b are constants. The work done in stretching this rubber band from x = 0 to x = L is: 4) When a certain rubber band is stretched a distance x, it exerts a restoring force F = ax + bx, where a 主 А) al?+ bLx В) al + 2bl? С) a + 2bL D) BL E) al?2 + bз

A man claiming a mountain carrying a bag with mass 7.5 kg , after 30 min he reach 8.2 m height from the start point. 1-calculate the work done from the man to the bag ? 2- if the man has weight 645 N , what is the work done while he carrying same bag ? 3-what is the energy difference between the man and the bag ?

A child of mass m = 16 kg slides down a slide of height h = 2.7 m without friction. Let gravitational potential energy be zero at ground level. a)Write an expression for the child's total mechanical energy, E, at the top of the slide, in terms of the variables in the problem and the acceleration due to gravity g.  b)Calculate the change in the child's potential energy, ΔU in joules, from the top to the bottom of the slide at ground level (i.e. ΔU = Uground - Utop).  c)What is the child's final speed, vf in m/s?

6.49 • Estimate how many 30 lb bags of mulch an average student in your physics class can load into the bed of a pickup truck in 5.0 min. The truck bed is 4.0 ft off the ground. If you assume that the magnitude of the work done on each bag by the student equals the magnitude of the work done on the bag by gravity when the bag is lifted into the truck, what is the average power output of the student? Express your result in watts and in horsepower.

6.2 • A tow truck pulls a car 5.00 km along a horizontal roadway using a cable having a tension of 850 N. (a) How much work does the cable do on the car if it pulls horizontally? If it pulls at 35.0° By above the horizontal? (b) Hlow much work does the cable do on the tow truck in both cases of part (a)? (c) How much work does grav- ity do on the car in part (a)?

30- A constant force of 100 N, which makes an angle of 37° with the horizontal plane, is applied to a stationary object in the horizontal plane, causing the object to be displaced by 10 m. How many J is the work done by the force? A) 798,6 B) 400,4 C) 254,8 D) 601,8 E) 0

→> In the figure, a constant force of magnitude 85.0 N is applied to a 7.0 kg shoe box at angle = 54.0°, causing the box to move up a frictionless ramp at constant speed. How much work is done on the box by when the box has moved through vertical distance h = 0.35 m? Number Units O 157

• A 1.50-kg book is sliding along a rough horizontal sur- face. At point A it is moving at 3.21 m/s, and at point B it has slowed to 1.25 m/s. (a) How much work was done on the book between A and B? (b) If –0.750 J of work is done on the book from B to C, how fast is it moving at point C? (c) How fast would it be moving at C if +0.750 J of work were done on it from B to C?