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Chapter 4: Q4.3-3PE (page 161)
A cleaner pushes a 4.50-kg laundry cart in such a way that the net external force on it is 60.0 N. Calculate the magnitude of its acceleration.
The magnitude of the acceleration is13.334 m/s2.
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The gravitational force on the basketball in Figure 4.6 is ignored. When gravity is taken into account, what is the direction of the net external force on the basketball鈥攁bove horizontal, below horizontal, or still horizontal.
To simulate the apparent weightlessness of space orbit, astronauts are trained in the hold of a cargo aircraft that is accelerating downward at g. Why will they appear to be weightless, as measured by standing on a bathroom scale, in this accelerated frame of reference? Is there any difference between their apparent weightlessness in orbit and in the aircraft?
Suppose two children push horizontally, but in exactly opposite directions, on a third child in a wagon. The first child exerts a force of 75.0 N, the second a force of 90.0 N, friction is 12.0 N, and the mass of the third child plus wagon is 23.0 kg.
(a) What is the system of interest if the acceleration of the child in the wagon is to be calculated?
(b) Draw a free-body diagram, including all forces acting on the system.
(c) Calculate the acceleration.
(d) What would the acceleration be if friction were 15.0 N?
(a) What is the strength of the weak nuclear force relative to the strong nuclear force?
(b) What is the strength of the weak nuclear force relative to the electromagnetic force?
Since the weak nuclear force acts at only very short distances, such as inside nuclei, where the strong and electromagnetic forces also act, it might seem surprising that we have any knowledge of it at all. We have such knowledge because the weak nuclear force is responsible for beta decay, a type of nuclear decay not explained by other forces.
Figure 4.39 shows Superhero and Trusty Sidekick hanging motionless from a rope. Superhero鈥檚 mass is 90.0 kg, while Trusty Sidekick鈥檚 is 55.0 kg, and the mass of the rope is negligible.
(a) Draw a free-body diagram of the situation showing all forces acting on Superhero, Trusty Sidekick, and the rope.
(b) Find the tension in the rope above Superhero.
(c) Find the tension in the rope between Superhero and Trusty Sidekick. Indicate on your free-body diagram the system of interest used to solve each part.
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