Ncert class 11 physics solutions 






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It decreases the separation between the two, thereby decreasing the potential energy of the body. All materials, however, have this same elastic property, but in most materials, it is not so pronounced. Similarly, while cutting fruits or vegetables, we make use of force and pressure. A tangential force F11 is applied at the top of the cube, a distance h above the bottom.
Calculate the height to which the block rises. Hence, external forces are able to change the energy of a system. Answer: a Positive In the given case, force and displacement are in the same direction. Walking applies physics concepts like principles of friction, weight, gravitational law, etc.
In this case, a complete transfer of momentum takes place from the moving mass to the stationary mass. Creating question papers online with your own name and logo takes less than 2 minutes. Hence, the work done is negative in this case. What is the work done by the gravitational force on the drop in the first and second half of its journey? Yet the work done by the gravitational force over every complete orbit of the comet is zero. Revision books, based on , for each chapter as well as notes of each chapter are available to download in pdf format. It will become zero i. First law of thermodynamics, isothermal and adiabatic processes. Equilibrium of concurrent forces, Static and kinetic friction, laws of friction, rolling friction, lubrication. The ratio of their speeds: Question 6. The international system of units was accepted in 1971 by the 14th general conference on Weights and Measures under the leadership of International Bureau of Weights and Measures, located at Paris in France.
NCERT solutions for class 11 Physics - Due to these reasons physics has intimate relationship with all the sciences and hence it is called a fundamental science.
When the force is removed the body returns to its original size and shape. Most people are familiar with the stretching of a rubber band. All materials, however, have this same elastic property, but in most materials, it is not so pronounced. The explanation of the elastic property of solids is found in an atomic description of a solid. Most solids are composed of a very large number of atoms or molecules arranged in a fixed pattern called the lattice structure of a solid and shown schematically in figure 1. These atoms or molecules are held in their positions by electrical forces. The electrical force between the molecules is attractive and tends to pull the molecules together. Thus, the solid resist being pulled apart. Any one molecule in figure 1 has an attractive force pulling it to the right and an equal attractive force pulling it to the left. There are also equal attractive forces pulling the molecule up and down, and in and out. A repulsive force between the molecules also tends to repel the molecules if they get too close together. This is why solids are difficult to compress. To explain this repulsive force we would need to invoke the Pauli exclusion principle of ncert class 11 physics solutions mechanics. If we try to pull one side of a solid material to the right, let us say, then we are in effect pulling all these molecules slightly away from their equilibrium position. The displacement of any one molecule from its equilibrium position is quite small, but since there are billions of molecules, the total molecular displacements are directly measurable as a change in length of the material. When the applied force is removed, the attractive molecular forces pull all the molecules back to their original positions, and the material returns to its original length. If we now exert a force on the material in order to compress it, we cause the molecules to be again displaced from their equilibrium position, but this time they are pushed closer together. The repulsive molecular force prevents them from getting too close together, but the total molecular displacement is directly measurable as a reduction in the size of the original material. When the compressive force is removed, the repulsive molecular force causes the atoms to return to their equilibrium position and the solid returns to its original size. Hence, the elastic properties of matter are a manifestation of the molecular forces that hold solids together. Figure 2 shows a typical lattice structure of atoms in a solar cell analyzed with a scanning tunneling microscope. Visualise the same concept and understand better, Click Physics for demos. If the body returns to its original shape when the distorting stress is removed, the body exhibits the property of elasticity of shape, sometimes called shear. A tangential force F11 is applied at the top of the cube, a distance h above the bottom. Fig 3 The magnitude of this force Ft times the height h of the cube would normally cause a torque to act on the cube to rotate it. However, since the cube is not free to rotate, the body instead becomes deformed and changes its shape, as shown in figure 3 The tangential force applied to the body causes the layers of atoms to be displaced sideways; one layer of the lattice structure slides over another. The tangential force thus causes a change in the shape of the body that is measured by the angle φ, called the angle of shear. We also find the deformation of the cube experimentally to be inversely proportional to the area of the top of the cube. With a larger area, the distorting force is spread over more molecules and hence the corresponding deformation is less. This implies that it is easier to slide ncert class 11 physics solutions of molecules over each other than it is to compress or stretch them. The shear modulus is also known as the torsion modulus and the modulus of rigidity.