Videos
(a)
The result of jumping from the second story balcony to the pavement below, landing stiff-legged on the feet.
(a)
Answer to Problem 1CQ
The person will incur injuries due to the large impulsive force acting on the person’s feet when he jumps from the second story balcony to the pavement below, landing stiff-legged on the feet.
Explanation of Solution
When a person is jumping from certain height, the possibilities of being injured internally depends primarily the average force acting to slow down the body. The impulsive force acting on the feet determines the likelihood of injuries.
The time interval for stopping for a person landing stiff legged on pavement is very short. Since the time interval is small, the average force acting on the person’s feet and other parts of leg is very large in accordance with the impulse-momentum theorem. The large impulsive force on the person’s feet and leg results the person to incur injuries when landing stiff legged on the pavement.
(b)
The result of a person jumping into a privet hedge, landing on his back and rolling to his feet.
(b)
Answer to Problem 1CQ
The likelihood of being injured upon jumping is very less when the person jumps into a privet hedge, landing on his back and rolling to his feet.
Explanation of Solution
When a person is jumping from certain height, the possibilities of being injured internally depends primarily the average force acting to slow down the body. The impulsive force acting on the feet determines the likelihood of injuries.
The time interval in stopping the person jumping into a privet hedge is high and as a result, the average force acting on the person’s torso is very low. Therefore, the likelihood of being injured upon jumping is very less when the person jumps into a privet hedge, landing on his back and rolling to his feet. However, the person may suffer superficial scratches.
(c)
The result of a person jumping into a firefighter’s net, landing on his back, and the method to increase the cushion the fall.
(c)
Answer to Problem 1CQ
The net stretches as the person falls into it, which increases the time interval in stopping the person. The person will not be injured during the event. In order to increase the cushion the person’s fall, the firefighter starts with the net held high and lower the net with their hands as the person lands.
Explanation of Solution
The firefighter’s net offers large time interval for bringing the person to rest. When the person falls in the net, the net stretches downward, gradually bringing the person to rest. The impulsive force in this situation is very low due to the large time interval.
In order to cushion the person’s fall, the firefighter starts with the net held high and lower the net with their hands as the person lands. This further extends the time interval during which the person is brought to rest.
Want to see more full solutions like this?
Chapter 7 Solutions
Physics
- Suppose there are two transformers between your house and the high-voltage transmission line that distributes the power. In addition, assume your house is the only one using electric power. At a substation the primary of a step-down transformer (turns ratio = 1:23) receives the voltage from the high-voltage transmission line. Because of your usage, a current of 51.1 mA exists in the primary of the transformer. The secondary is connected to the primary of another step-down transformer (turns ratio = 1:36) somewhere near your house, perhaps up on a telephone pole. The secondary of this transformer delivers a 240-V emf to your house. How much power is your house using? Remember that the current and voltage given in this problem are rms values.arrow_forwardThe human eye is most sensitive to light having a frequency of about 5.5 × 1014 Hz, which is in the yellow-green region of the electromagnetic spectrum. How many wavelengths of this light can fit across a distance of 2.2 cm?arrow_forwardA one-dimensional harmonic oscillator of mass m and angular frequency w is in a heat bath of temperature T. What is the root mean square of the displacement of the oscillator? (In the expressions below k is the Boltzmann constant.) Select one: ○ (KT/mw²)1/2 ○ (KT/mw²)-1/2 ○ kT/w O (KT/mw²) 1/2In(2)arrow_forward
- Two polarizers are placed on top of each other so that their transmission axes coincide. If unpolarized light falls on the system, the transmitted intensity is lo. What is the transmitted intensity if one of the polarizers is rotated by 30 degrees? Select one: ○ 10/4 ○ 0.866 lo ○ 310/4 01/2 10/2arrow_forwardBefore attempting this problem, review Conceptual Example 7. The intensity of the light that reaches the photocell in the drawing is 160 W/m², when 0 = 18°. What would be the intensity reaching the photocell if the analyzer were removed from the setup, everything else remaining the same? Light Photocell Polarizer Insert Analyzerarrow_forwardThe lifetime of a muon in its rest frame is 2.2 microseconds. What is the lifetime of the muon measured in the laboratory frame, where the muon's kinetic energy is 53 MeV? It is known that the rest energy of the muon is 106 MeV. Select one: O 4.4 microseconds O 6.6 microseconds O 3.3 microseconds O 1.1 microsecondsarrow_forward
- The Lagrangian of a particle performing harmonic oscil- lations is written in the form L = ax² - Bx² - yx, where a, and are constants. What is the angular frequency of oscillations? A) √2/a B) √(+2a)/B C) √√Ba D) B/αarrow_forwardThe mean temperature of the Earth is T=287 K. What would the new mean temperature T' be if the mean distance between the Earth and the Sun was increased by 2%? Select one: ○ 293 K O 281 K ○ 273 K 284 Karrow_forwardTwo concentric current-carrying wire loops of radius 3 cm and 9 cm lie in the same plane. The currents in the loops flow in the same direction and are equal in magnitude. The magnetic field at the common center of the loops is 50 mT. What would be the value of magnetic field at the center if the direction of the two currents was opposite to each other (but their value is kept constant)? Select one: ○ 20 mT ○ 10 mT O 15 mT ○ 25 mTarrow_forward
- An ideal coil of inductivity 50 mH is connected in series with a resistor of 50 ohm. This system is connected to a 4.5 V battery for a long time. What is the current in the circuit? Select one: O 45 mA ○ 90 mA 00 mA O 150 mAarrow_forwardThere are two thin-walled spherical shells made from the same material, the radius of the smaller shell is half of the radius of the larger one. The thickness of the walls is the same. Denote the moment of inertia (with respect to the center) of the larger shell by I₁, and that of the smaller one by 12. What is the ratio I₁/12? Select one: ○ 8 O 16 O 4 ○ 32arrow_forwardA swimming pool has dimensions 20.0 m X 20.0 m and a flat bottom. The pool is filled to a depth of 3.00 m with fresh water. By what force does the water push each of the sidewalls? Density of water is 1000 kg/m³. Select one: ○ ~ 900 KN о ~ 2 ~ 1800 kN 600 kN 1500 kNarrow_forward
College PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning
University Physics (14th Edition)PhysicsISBN:9780133969290Author:Hugh D. Young, Roger A. FreedmanPublisher:PEARSON
Introduction To Quantum MechanicsPhysicsISBN:9781107189638Author:Griffiths, David J., Schroeter, Darrell F.Publisher:Cambridge University Press
Physics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning
Lecture- Tutorials for Introductory AstronomyPhysicsISBN:9780321820464Author:Edward E. Prather, Tim P. Slater, Jeff P. Adams, Gina BrissendenPublisher:Addison-Wesley
College Physics: A Strategic Approach (4th Editio...PhysicsISBN:9780134609034Author:Randall D. Knight (Professor Emeritus), Brian Jones, Stuart FieldPublisher:PEARSON