Irina Lyublinskaya, Gregg Wolfe, Douglas Ingram , Liza Pujji
ISBN #9781938168932
2,282 Questions
Homework Questions
This section explores the interactions of forces such as friction, drag, and elasticity. Friction is examined as both static and kinetic, highlighting its dependence on the normal force and material properties. Drag forces, which oppose the motion through fluids, are analyzed through quadratic relationships with speed and are crucial in understanding terminal velocity. Finally, elasticity is discussed via Hooke’s law, stress, and strain, providing insight into how materials deform under forces and how properties like Young’s modulus determine a material's stiffness.
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A physics major is cooking breakfast when he notices that the frictional force between his steel spatula and his Teflon frying pan is only 0.200 $\mathrm{N}$ . Knowing the coefficient of kinetic friction between the two materials, he quickly calculates the normal force. What is it?
(a) When rebuilding her car's engine, a physics major must exert 300 $\mathrm{N}$ of force to insert a dry steel piston into a steel cylinder. What is the magnitude of the normal force between the piston and cylinder? (b) What is the magnitude of the force would she have to exert if the steel parts were oiled?
(a) What is the maximum frictional force in the knee joint of a person who supports 66.0 kg of her mass on that knee? (b) During strenuous exercise it is possible to exert forces to the joints that are easily ten times greater than the weight being supported. What is the maximum force of friction under such conditions? The frictional forces in joints are relatively small in all circumstances except when the joints deteriorate, such as from injury or arthritis. Increased frictional forces can cause further damage and pain.
Suppose you have a 120-kg wooden crate resting on a wood floor. (a) What maximum force can you exert horizontally on the crate without moving it? (b) If you continue to exert this force once the crate starts to slip, what will the magnitude of its acceleration then be?
(a) If half of the weight of a small $1.00 \times 10^{3}$ kg utility truck is supported by its two drive wheels, what is the magnitude of the maximum acceleration it can achieve on dry concrete? (b) Will a metal cabinet lying on the wooden bed of the truck slip if accelerates at this rate? (c) Solve both problems assuming the truck has four-wheel drive.