Physics MCQs for NEET — Practice Questions with Answers

For uniform velocity, the net force on the body is zero. This means the applied force must be equal in magnitude and opposite in direction to the frictional force. The applied force acts in the direction of motion, doing positive work. The frictional force acts opposite to the direction of motion, doing negative work. Since the body moves with uniform velocity, the work done by the applied force must be equal in magnitude to the negative work done by friction, so that net work done is zero, and thus change in kinetic energy is zero (as velocity is constant). The NCERT exercise mentions 'work done by an applied force on a body moving on a rough horizontal plane with uniform velocity' and 'work done by friction on a body sliding down an inclined plane' (which implies negative work for friction). Hence, the applied force does positive work, and friction does negative work of equal magnitude.

According to the NCERT text, 'Work done is a scalar quantity. It can be positive or negative unlike mass and kinetic energy which are positive scalar quantities.' Potential energy is undetermined up to a constant and can be positive, negative, or zero depending on the choice of reference point. Displacement is a vector quantity and its component can be positive or negative.

The provided text states, 'The elastic behaviour of materials plays an important role in engineering design. For example...Can we design an aeroplane which is very light but sufficiently strong?' This directly links the elastic behavior of materials to the design of light yet strong structures like airplane wings.

The text poses the question: 'Why does a railway track have a particular shape like I?' While the direct answer isn't given, implicitly, this shape is chosen due to elastic behavior considerations to withstand forces efficiently. I-beams are engineered to have high strength-to-weight ratios, resisting bending and buckling effectively, which is a key application of elastic behavior in structural design.

The 'POINTS TO PONDER' section clarifies: 'In daily life, we feel that a material which stretches more is more elastic, but it is a misnomer. In fact, material which stretches to a lesser extent for a given load is considered to be more elastic.' This contradicts common intuition and highlights the scientific definition of elasticity.

The text states, 'The elastic behaviour of materials plays an important role in engineering design. For example, while designing a building, knowledge of elastic properties of materials like steel, concrete etc. is essential.' This indicates that understanding how these materials deform under stress and return to their original shape is crucial for structural integrity and safety.

The 'POINTS TO PONDER' section notes: 'A material with large value of Young’s modulus requires a large force to produce small changes in its length.' This property is desirable for structural components where minimal deformation under stress is critical.

The 'POINTS TO PONDER' section explicitly states: 'Metals have larger values of Young’s modulus than alloys and elastomers.' Also, 'Young’s modulus and shear modulus are relevant only for solids since only solids have lengths and shapes.'

The text asks, 'Can we design an artificial limb which is lighter but stronger?' This question highlights the practical application of elastic properties in balancing weight and strength for improved user experience and functionality in prosthetics.

The text states, 'The same is true in the design of bridges, automobiles, ropeways etc.' This implies that, similar to structures like bridges, ropeways rely on the elastic behavior of strong solid materials (like steel cables) to safely support loads and withstand stresses.