Suppose a person uses a mechanical jack to lift one half the weight of a car with a mass of 1200 kg. During each stroke of the jack handle, the person’s hand is pushing for a distance of 40.0 cm but the car is lifted only 5.0 mm. (a) Assuming the jack is 100% efficient, how much force must the person exert on the handle as the car is lifted? (b) If the actual amount of force required on the handle is 90.0 N, what is the actual efficiency of the jack

Suppose a person uses a mechanical jack to lift one half the weight of a car with a mass of 1200 kg. During each stroke of the jack handle, the person’s hand is pushing for a distance of 40.0 cm but the car is lifted only 5.0 mm. (a) Assuming the jack is 100% efficient, how much force must the person exert on the handle as the car is lifted? (b) If the actual amount of force required on the handle is 90.0 N, what is the actual efficiency of the jack

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter5: Newton's Laws Of Motion

Section: Chapter Questions

Problem 48PQ: To get in shape, you head to the local gym to exercise by lifting weights. Using a lat machine (Fig....

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To get in shape, you head to the local gym to exercise by lifting weights. Using a lat machine (Fig. P5.48), you notice that the wire connected to the bar is run around three different pulleys and is connected to a vertical stack of weights on the other end. The weights move up and down as you pull down on the bar. Suppose you set the machine so that the weight to be lifted is 120.0 lb. When you pull down on the bar, exerting a constant force, the acceleration experienced by the weights is 0.250 m/s2. What tension must exist in the wire connecting the bar and weights under these conditions? Assume the pulleys are massless and frictionless. FIGURE P5.48
A man stands on his toes by exerting an upward force through the Achilles tendon, as in the figure. Calculate the force in the Achilles tendon if he stands on one foot and has a mass of 80kg.
When you lift an object by moving only your forearm, the main lifting muscle in your arm is the biceps. Suppose the mass of a forearm with hand is 1.60 kg. If the biceps is connected to the forearm a distance of 2.4 cm from the elbow, how much force must the biceps exert to hold a 42 N ball at the end of the forearm at distance of 36.0 cm from the elbow, with the forearm parallel to the floor, in Newtons? Use g = 10.0 m/s2. Your answer needs to have 3 significant figures, including the negative sign in your answer if needed. Do not include the positive sign if the answer is positive. No unit is needed in your answer, it is already given in the question statement.
When you lift an object by moving only your forearm, the main lifting muscle in your arm is the biceps. Suppose the mass of a forearm with hand is 1.60 kg. If the biceps is connected to the forearm a distance of 2.1 cm from the elbow, how much force must the biceps exert to hold a 37 N ball at the end of the forearm at distance of 36.0 cm from the elbow, with the forearm parallel to the floor, in Newtons? Use g = 10.0 m/s2.
Suppose you use an ideal pulley of the type shown in Figure 5.18(a) to support a car engine of mass 110 kg. What force must the ceiling supply, assuming you pull straight down on the rope? Neglect the pulley system's mass. N (upward)
Suppose you use an ideal pulley of the type shown in Figure 5.18(a) to support a car engine of mass 120 kg. (see attached photo) (a) What would the tension in the rope be? ....................N(b) What force must the ceiling supply, assuming you pull straight down on the rope? Neglect the pulley system's mass. ...................N (upward)
When you lift an object by moving only your forearm, the main lifting muscle in your arm is the biceps. Suppose the mass of a forearm is 1.30 kg . If the biceps is connected to the forearm a distance dbiceps = 3.00 cm from the elbow, how much force Fbiceps must the biceps exert to hold a 750 g ball at the end of the forearm at distance dball = 35.0 cm from the elbow, with the forearm parallel to the floor? How much force Felbow must the elbow exert? What is the horizontal distance dforearm between the elbow and the point where the weight of the forearm acts?
When you lift an object by moving only your forearm, the main lifting muscle in your arm is the biceps. Suppose the mass of a forearm is 1.30 kg . If the biceps is connected to the forearm a distance dbiceps = 3.00 cm from the elbow, how much force Fbiceps must the biceps exert to hold a 750 g ball at the end of the forearm at distance dball = 35.0 cm from the elbow, with the forearm parallel to the floor? How much force Felbow must the elbow exert? (Figure 1)
If you push a box across a floor it’s “physical work” but if you push on the wall it’s not. Which of the following choices explains why?
A lever has the following dimensions: Resistive force distance: 15 cmEffort force distance: 85 cm If you can exert a maximum effort force of 800 N, what is the maximum resistive force you can lift with the lever?
For serious fractures of the leg, the leg may need to have a stretching force applied to it to keep contracting leg muscles from forcing the broken bones together too hard. This is often done using traction, an arrangement of a rope, a weight, and pulleys as shown. The rope must make the same angle u on both sides of the pulley so that the net force of the rope on the pulley is horizontally to the right, but θ can be adjusted to control the amount of traction. The doctor has specified 50 N of traction for this patient, with a 4.2 kg hanging mass. What is the proper angle θ?
A box is given a push so that it slides across the floor. How far will it go, given that the coefficient of kinetic friction is 0.18 and the push imparts an initial speed of 3.9 m/sm/s ? Express your answer to two significant figures and include the appropriate units.