A kg truck is parked on a slope. How big is the friction force on the truck? The coefficient of static friction between the tires and the road is .
The friction force on the truck is .
The friction force is equal to the product of the coefficient of friction and the normal force. The force that stops one solid object from sliding or rolling over another is known as friction. Frictional forces, such as the traction needed to walk without slipping, can be beneficial, but they can cause a lot of resistance to movement.
Let the horizontal weight force is and vertical weight force is .
According to Newton's second law of motion, the friction force can be written as
Here we are given
Substitute the vales , here, is the friction force, is the coefficient of static between friction force, is the normal force
You're driving along at with your aunt's valuable antiques in the back of your pickup truck when suddenly you see a giant hole in the road ahead of you. Fortunately, your foot is right beside the brake and your reaction time is zero!
a. Can you stop the truck before it falls into the hole?
b. If your answer to part a is yes, can you stop without the antiques sliding and being damaged? Their coefficients of friction are and .
Large objects have inertia and tend to keep moving-Newton's BI0 first law. Life is very different for small microorganisms that swim through water. For them, drag forces are so large that they instantly stop, without coasting, if they cease their swimming motion. To swim at constant speed, they must exert a constant propulsion force by rotating corkscrew-like flagella or beating hair-like cilia. The quadratic model of drag of Equation fails for very small particles. Instead, a small object moving in liquid experiences a linear drag force, , the direction opposite the motion), where is a constant. For a sphere of radius , the drag constant can be shown to be , where is the viscosity of the liquid. Water at has viscosity .
a. A paramecium is about long. If it's modeled as a sphere, how much propulsion force must it exert to swim at a typical speed of ? How about the propulsion force of a --diameter . coli bacterium swimming at ?
b. The propulsion forces are very small, but so are the organisms. To judge whether the propulsion force is large or small relative to the organism, compute the acceleration that the propulsion force could give each organism if there were no drag. The density of both organisms is the same as that of water, .
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