Concept explainers
* BIO Bone break The tibia bone in the lower leg of an adult human will break if the compressive force on it exceeds about
N (we assume that the ankle is pushing up). Suppose that a student of mass 60 kg steps off a chair that is 0.40 m above the floor. If landing stiff-legged on the surface below, what minimum stopping distance does he need to avoid breaking his tibias? Indicate any assumptions you made in your answer to this question.
Want to see the full answer?
Check out a sample textbook solutionChapter 7 Solutions
College Physics
Additional Science Textbook Solutions
Introduction to Electrodynamics
College Physics: A Strategic Approach (4th Edition)
University Physics Volume 1
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
University Physics (14th Edition)
Tutorials in Introductory Physics
- Review. A force platform is a tool used to analyze the performance of athletes by measuring the vertical force the athlete exerts on the ground as a function of time. Starting from rest, a 65.0-kg athlete jumps down onto the platform from a height of 0.600 m. While she is in contact with the platform during the time interval 0t 0.800 s, the force she exerts on it is described by the function F = 9 200t 11 500 t2 where F is in newtons and t is in seconds. (a) What impulse did the athlete receive from the platform? (b) With what speed did she reach the platform? (c) With what speed did she leave it? (d) To what height did she jump upon leaving the platform?arrow_forwardA roller-coaster car (Fig. P6.16) has a mass of 500 kg when fully loaded with passengers. The path of the ca coaster from its initial point shown in the figure to point involves only up-and-down motion (as seen by the riders), with no motion to the left or right, (a) If the vehicle has a speed of 20.0 m/s at point . what is the force exerted by the track on the car at this point? (b) What is the maximum speed the vehicle can have at point and still remain on the track? Assume the roller-coaster tracks at points andl are parts of vertical circles of radius r1 = 10.0 m and i2 = 15.0 m, respectively.arrow_forward(a) Calculate the force needed to bring a 950-kg car to rest from a speed of 90.0 km/h in a distance of 120 m (a fairly typical distance for a non-panic stop). (b) Suppose instead the car hits a concrete abutment at full speed and is brought to a stop in 2.00 m. Calculate the force exerted on the car and compare it with the force found in part (a).arrow_forward
- (a) A child slides down a water slide at an amusement park from an initial height h. The slide can be considered frictionless because of the water flowing down it. Can the equation for conservation of mechanical energy be used on the child? (b) Is the mass of the child a factor in determining his speed at the bottom of the slide? (c) The child drops straight down rather than following the curved ramp of the slide. In which case will he be traveling faster at ground level? (d) If friction is present, how would the conservation-of-energy equation be modified? (e) Find the maximum speed of the child when the slide is frictionless if the initial height of the slide is 12.0 m.arrow_forwardProfessional Application If you dive into water, you reach greater depths if you do a belly flop. Explain this difference in depth using the concept of conservation of energy. Explain this difference in depth using what you have learned in this chapter.arrow_forward1.) You know your mass is 64 kgkg , but when you stand on a bathroom scale in an elevator, it says your mass is 87 kgkg . What is the acceleration of the elevator? Express your answer using three significant figures and include the appropriate units. a=__________ ____________ In which direction is the acceleration of the elevator? upward or downward 2.) In the high jump, the kinetic energy of an athlete is transformed into gravitational potential energy without the aid of a pole. With what minimum speed must athlete leave the ground in order to lift his center of mass 1.85 mm and cross the bar with a speed of 0.85 m/sm/s ? Express your answer to two significant figures and include the appropriate units. v=_________ ___________arrow_forward
- Suppose a car approaches a hill and has an initial speed of 120 km/h at the bottom of the hill. The driver takes her foot off of the gas pedal and allows the car to coast up the hill. Note: the 790-kg car with an initial speed of 120 km/h is observed to coast up a hill and stops at a height 21 m above its starting point. a.) What is the magnitude of the average force of friction, in newtons, if the hill has a slope 2.7° above the horizontal?arrow_forward3. A block of mass 3.8 kg is sitting on a frictionless ramp with a spring at the bottom that has a spring constant of 695 N/m (refer to the figure). The angle of the ramp with respect to the horizontal is 37°. Part (a) The block, starting from rest, slides down the ramp a distance 65 cm before hitting the spring. How far, in centimeters, is the spring compressed as the block comes to momentary rest? Part (b) After the block comes to rest, the spring pushes the block back up the ramp. How fast, in meters per second, is the block moving right after it comes off the spring? Part (c) What is the change of the gravitational potential energy, in joules, between the original position of the blockarrow_forwardCalculate the work done by friction as a 3.7 kg box is slid along a floor from point A to point B in the figure along paths 1, 2, and 3. Assume that the coefficient of kinetic friction between the box and the floor is 0.19. (Figure 1) Enter your answers numerically separated by commas. Express your answers using two significant figures. W1,W2,W3= ______ Jarrow_forward
- Two flat stone blocks of masses 100kg each are stacked on top of one another on the back of a truck. The coefficient of static friction between the bottom block and the truck is 0.8 and between the two blocks is 0.7. (Describe how you get the answers per question!) a) What is the maximum acceleration the truck can have such that neither of the blocks slide off ? b) If the truck accelerates from rest at this maximum acceleration for 6 seconds, how much more energy will the truck's engine need to output compared to if the stone blo cks were not on the truck? c) What is the maximum speed that the truck can drive around a curve of minimum curvature radius 100m without either of the blocks sliding off ? d) What is the maximum slope that the truck can drive up at constant speed without either of the blocks sliding off?arrow_forwardA 0.160 kg hockey puck starts from rest and reaches a speed of 22 m/s when a hockey stick pushes on it for 1.2 m during a shot. (a) What is the final kinetic energy of the puck? (b) Determine the average net force on the puck using two different methods.arrow_forwardA 400 gram rock is thrown vertically upwards from the surface of Earth. When it is 14 m above the ground, it is traveling upwards at 24 m/s. 1) Draw a sketch of the situation, labeling all of the physical quantities given in the problem. Identify your system in the sketch. Make sure all relevant moments in time are shown in your sketch. 2) Draw a work energy bar chart where the system is the rock and Earth.arrow_forward
- Classical Dynamics of Particles and SystemsPhysicsISBN:9780534408961Author:Stephen T. Thornton, Jerry B. MarionPublisher:Cengage LearningCollege PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningPhysics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
- College PhysicsPhysicsISBN:9781938168000Author:Paul Peter Urone, Roger HinrichsPublisher:OpenStax CollegePhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningPhysics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning