Concept explainers
The tray dispenser in your cafeteria has broken and is not repairable. The custodian knows that you are good at designing things and asks you to help him build a new dispenser out of spare parts he has on his workbench. The tray dispenser supports a stack of trays on a shelf that is supported by four springs, one at each corner of the shelf. Each tray is rectangular, with dimensions 45.3 cm by 35.6 cm. Each tray is 0.450 cm thick and has a mass of 580 g. The custodian asks you to design a new four-spring dispenser such that when a tray is removed, the dispenser pushes up the remaining stack so that the top tray is at the same position as the just-removed tray was. He has a wide variety of springs that he can use to build the dispenser. Which springs should he use?
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Chapter 7 Solutions
Physics for Scientists and Engineers with Modern Physics
- An 8.0-cm-long spring is attached to the ceiling. When a 2.3 kg mass is hung from it, the spring stretches to a length of 16 cm. How long is the spring when a 3.0 kg mass is suspended from it? y=arrow_forwardA board sits in equilibrium. On the left end, there is a wire that supports the board from the ceiling, and to the right, there is a sawhorse that supports the board from the ground. The sawhorse is a distance d= 1/5l from the right edge of the board. There is a block with mass ms= 4.5kg that is a distance 3/4l from the right edge of the board. Finally the board has a mass mb= 11kg. e) What is the force of tension and normal force on the board?arrow_forwardA board sits in equilibrium. On the left end, there is a wire that supports the board from the ceiling, and to the right, there is a sawhorse that supports the board from the ground. The sawhorse is a distance d= 1/5l from the right edge of the board. There is a block with mass ms= 4.5kg that is a distance 3/4l from the right edge of the board. Finally the board has a mass mb= 11kg. e) What is the force of tension and normal force on the board?arrow_forward
- Consider the following figure. A strand has one end tied to a wall, extends across a small fixed pulley, and the other end is tied to a hanging object. M The total length of the strand is L = 9.00 m, the mass of the strand is m = 9.00 g, the mass of the hanging object is M = 7.00 kg, and the pulley is a fixed a distance d = 7.00 m from the walI. You pluck the strand between the wall and the pulley and it starts to vibrate. What is the fundamental frequency (in Hz) of its vibration? 19.40 How is the speed of the wave along the strand related to the tensions in and the linear mass density? How is the speed of the wave along the strand related to the wavelength and the frequency? See if you can combine these two relationships to determine the desired frequency. Hz Need Help? Read Itarrow_forwardA person opens a door by applying a 13-N force perpendicular to it at a distance 0.90 m from the hinges. The door is pushed wide open (to 120 ° ) in 2.6 s How much work was done? Express your answer using two significant figures. να ΑΣφ J Submit Request Answer Part B What was the average power delivered? Express your answer using two significant figures. Hνα ΑΣφarrow_forwardA ladder of negligible mass composed of two L-long rails that are hinged at the top, is placed on top of a frictionless floor. A metal bar, connecting both rails halfway up the ladder is placed so that the two rails make an angle of 0 = 43.0 at the apex. Lastly, a M = 4.30 [kg] block is placed 2/3 of the way up the ladder, as shown. 213 L Ө L H # A) what is the magnitude of the tension in the metal bar? B) What is the magnitude of the normal force exerted on the bottom right side of the ladder? C) What is the magnitude of the normal force exerted on the bottom left side of the ladder? D) What is the magnitude of the force the right side of the ladder exerts on its left side?arrow_forward
- For given two vectors, Ā = -2.01 + 3.0f + 4.0k and B = 3.0î + 1.0j – 3.0k a. Find the cross product (Ā x B) of these vectors. Give a specific Physical example that is explained by cross product. b. Find the scalar product (Ā. B) of these vectors. Give a specific Physical example that is explained by dot product. c. Find the angle between these two vectors? d. Explain scalar and vector quantities in detail. Give at least two examples for each quantity.arrow_forwardB. A couple of 500 Joule is applied on a box counter-clockwise. Compute the force F of the Couple if the perpendicular distance is along through C and F.arrow_forwardScissors are like a double-lever "Stem, Which of the Simple machines in Figure 9.23 and Figure 9.24 is most analogous to scissors? Figure 9.23 A nail puller is a lever with a large mechanical advantage. The external forces on the nail puller are represented by solid arrows. The force that the nail puller applies to the nail ( Fo ) is not a force on the nail puller. The reaction force the nail exerts back on the puller ( Fn ) is an external force and is equal and opposite to Fo. The perpendicular lever arms of the input and output forces are li and l0 Figure 9.24 (a) In the case of the wheelbarrow, the output force or load is between the pivot and the input force. The pivot IS the wheel's axle. Here, the output force is greater than the input force. Thus, a wheelbarrow enables you to lift much heavier loads than you could with your body alone. (b) In the case of the shovel, the input force is between the pivot and the load, but the input lever arm is shorter than the output lever arm. The pivot is at the handle held by the right hand. Here, the output force (supporting the shovel's load) is less than the input force (from the hand nearest the load), because the Input is exerted closer to the pivot than is the outputarrow_forward
- Proof that the energy stored in the compact bone is given by E = AL0 (Sb) ^ 2 / 2γ. When Sb is bone stress. *arrow_forwardA student in a physics lab is asked to classify two springs. Right away, they notice some differences. The first spring, spring 1, is very easy to compress and pliable. The second spring, spring 2, is stiffer and more difficult to deform. Now, the student wants to understand the springs quantitatively. It takes 10.0 J10.0 J of work to stretch spring 1 by 12.0 cm.12.0 cm. 20.0 J20.0 J is required to displace the second spring 3.00 cm.3.00 cm. What is the ratio of the two spring constants, ?2/?1?k2/k1? ?1k1 is the spring constant of spring 1, and ?2k2 is the spring constant of spring 2.arrow_forwardTruck suspensions often have "helper springs" that engage at high loads. One such arrangement is a leaf spring with a helper coil spring mounted on the axle, as shown in the figure below. When the main leaf spring is compressed by distance yo, the helper spring engages and then helps to support any additional load. Suppose the leaf spring constant is 4.90 x 105 N/m, the helper spring constant is 3.60 x 105 N/m, and yo = 0.500 m. Truck body Axle (a) What is the compression of the leaf spring for a load of 4.70 x 105 N? 0.87 Your response differs from the correct answer by more than 10%. Double check your calculations. m (b) How much work is done in compressing the springs? 0.855 Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully. Jarrow_forward
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