In a traction setup for a broken bone, with pulleys and rope available, how might we be able to increase the force along the femur using the same weight? (See Figure 4.30.) (Note that the femur is the shin bone shown in this image.
The force can be increased or decreased using the same weight using pulleys and ropes.
Whatever supports a load, it must supply an upward force equal to the weight of the load. This upward force is called the normal force.
Referring to figure 4.30, the traction setup shown helps in increasing the force across the broken bone using ropes and pulleys. By changing the angle shown in the figure, the magnitude of the force can be increased because as the value of is increased , the value of also increases.
Hence, the force can be increased or decreased using the same weight.
Near the end of a marathon race, the first two runners are separated by a distance of 45 m. The front runner has a velocity of 3.50 m/s, and the second a velocity of 4.20 m/s. (a) what is the velocity of the second runner relative to the first? (b) If the front runner is 250 m from the finish line, who will win the race, assuming they run at constant velocity? (c) What distance ahead will the winner be when she crosses the finish line?
A 2.50-kg fireworks shell is fired straight up from a mortar and reaches a height of 110 m.
(a) Neglecting air resistance (a poor assumption, but we will make it for this example), calculate the shell’s velocity when it leaves the mortar.
(b) The mortar itself is a tube 0.450 m long. Calculate the average acceleration of the shell in the tube as it goes from zero to the velocity found in (a).
(c) What is the average force on the shell in the mortar? Express your answer in newtons and as a ratio to the weight of the shell.
Consider two people pushing a toboggan with four children on it up a snow-covered slope. Construct a problem in which you calculate the acceleration of the toboggan and its load. Include a free-body diagram of the appropriate system of interest as the basis for your analysis. Show vector forces and their components and explain the choice of coordinates. Among the things to be considered are the forces exerted by those pushing, the angle of the slope, and the masses of the toboggan and children.
Consider the baby being weighed in Figure 4.34.
(a) What is the mass of the child and basket if a scale reading of 55 N is observed?
(b) What is the tension T1 in the cord attaching the baby to the scale?
(c) What is the tension T2 in the cord attaching the scale to the ceiling, if the scale has a mass of 0.500 kg?
(d) Draw a sketch of the situation indicating the system of interest used to solve each part. The masses of the cords are negligible.
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