Concept explainers
* Evaluation question You find the following in a report about blackouts: "The acceleration that causes blackouts in fighter pilots is called the maximum g-force. Fighter pilots experience this force when accelerating or decelerating quickly. At high fir's, the pilot’s blood pressure changes and the flow of oxygen to the brain rapidly decreases. This happens because the pressure outside of the pilot's body is so much greater than the pressure a human is normally accustomed to." Indicate any incorrect physics (including the application of physics to biology) that you find.
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College Physics: Explore And Apply, Volume 2 (2nd Edition)
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- A team of eight dogs pulls a sled with waxed wood runners on wet snow (mush!). The dogs have average masses of 19.0 kg, and the loaded sled with its rider has a mass of 210 kg. (a) Calculate the magnitude of the acceleration starting from rest if each dog exerts an average force of 185 N backward on the snow. (b) What is the magnitude of the acceleration once the sled starts to move? (c) For both situations, calculate the magnitude of the force in the coupling between the dogs and the sled.arrow_forwardAn inflated spherical beach ball with a radius of 0.3573 m and average density of 10.65 kg/m3 is being held under water in a pool by Janelle. The density of the water in the pool is 1000.0 kg/m3. When Janelle releases the ball, it begins to rise to the surface. If the drag coefficient of the ball in the water is 0.470 and the constant upward force on the ball is 1875 N, what will be the terminal speed of the ball as it rises? Ignore the effects of gravity on the ball.arrow_forwardReview. A rifle bullet with a mass of 12.0 g traveling toward the right at 260 m/s strikes a large hag of sand and penetrates it to a depth of 23.0 cm. Determine the magnitude and direction of the friction force (assumed constant) that acts on the bullet.arrow_forward
- Elisha Graves Otis invented the elevator brake in the mid-1800s, making it possible to build tall skyscrapers with fast elevators. Todays skyscrapers are a large fraction of a mile tall; for example. Taipei 101 in Taiwan has 101 stories and is 515 m (0.32 miles) tall. The top speed of the elevator in the Taipei 101 tower is roughly three times greater than the ascent rate of a commercial jet airplane. The position and time data in the table are based on such an elevator. a. Working in SI units, make a position-versus-time graph for the elevator. (You may wish to use a spreadsheet program.) b. Describe the motion of the elevator in words. c. Find the highest speed of the elevator. When is the elevator going at this speed? d. What sort of considerations would the engineers need to make to ensure the comfort of the passengers?arrow_forwardPhysics Review A soap bubble hovers motionlessly in the air. If the soap bubbles mass, including the air inside it, is 2.00 104 kg determine the magnitude of the upward force acting on it. (See Section 4.5.)arrow_forwardWhich of the following statements is correct?a.The coefficient of kinetic friction is typically greater than the coefficient of static friction. b.The coefficient of static friction is always less than c.The coefficient of static and kinetic friction are always equal. d.The coefficient of static friction is typically greater than the coefficient of kinetic friction. It states that the elongation is proportional to the force.a.Young's theorem b.Pascal's law c.Farrell's law d.Hooke's law The negative value of the work done by gravity on the body is the ____ of the body. a.gravitational potential energy b.Gravitational kinetic energy c.Net gravitational energy d.Negative gravitational energyarrow_forward
- QUESTION 1 Problem Like friction, drag force opposes the motion of a particle in a fluid; however, drag force depends on the particle's velocity. Find the expression for the particle's velocity v(x) as a function of position at any point x in a fluid whose drag force is expressed as Fdrag = kmv where k is a constant, m is the mass of the particle and v is its velocity. Assume that the particle is constrained to move in the x-axis only with an initial velocity vo. Solution: The net force along the x-axis is: EF = -F then: mv = m Since acceleration is the first time derivative of velocity a = dv/dt, mv = m We can eliminate time dt by expressing, the velocity on the left side of the equation as v= dx/dt. Manipulating the variables and simplifying, we arrive at the following expression = -k "Isolating" the infinitesimal velocity dx and integrating with respect to dx, we arrive at the following: = v - which shows that velocity decreases in a linear manner.arrow_forwardQ2/What is the purpose of having the negative sign in? Hooke's Lawarrow_forwardQUESTION 1 Problem Like friction, drag force opposes the motion of a particle in a fluid; however, drag force depends on the particle's velocity. Find the expression for the particle's velocity v(x) as a function of position at any point x in a fluid whose drag force is expressed as Fdrag = kmv where k is a constant, m is the mass of the particle and v is its velocity. Assume that the particle constrained to move in the x-axis only with an initial velocity vo. Solution: The net force along the x-axis is: ΣF-F = m then: mv - m Since acceleration is the first time derivative of velocity a = dv/dt, mv = m We can eliminate time dt by expressing, the velocity on the left side of the equation as v= dx/dt. Manipulating the variables and simplifying, we arrive at the following expression = -k "Isolating" the infinitesimal velocity dx and integrating with respect to dx, we arrive at the following: = v0 which shows that velocity decreases in a linear manner.arrow_forward
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