7 Un oggetto si sta muovendo di moto rettilineo uniforme lungo un asse orientato. Se la legge ora- ria del moto è \( s=20 t-10 \), dove \( s \) è espresso in metri e \( t \) in secondi, è vero che: (a) per \( t=0 \) l'oggetto si trova nel semiasse negativo (b) l'oggetto transita in corrispondenza dellorigine dell'asse per \( t=1 \mathrm{~s} \) (c) la velocità dell'oggetto cresce con il trascorrere del tempo (d) la velocità dell'oggetto è costante e vale \( 2 \mathrm{~m} / \mathrm{s} \) (e) Nessuna delle precedenti affermazioni è corretta

4) Suppose a uniform electric field exists in the room in which you are working, suc at the lines of force are horizontal and at right angles to one wall. As you walk towar e wall from which the lines of force emerge into the room, are you walking toward Points of lower potential Points of the same potential (equipotential line)? All Choices Are Wrong 5) Which of these statements is not characteristic of a static magnetic field? It is solenoidal. Magnetic flux lines are always closed. It has no sinks or sources All Choices Are Wrong

2) By saying that the electrostatic field is conservative, we do not mean that All Choices Are Wrong The potential difference between any two points is zero. lts circulation is identically zero. Its curl is identically zero. It is the gradient of a scalar potential.

एक सरल आवर्ती दोलक की गतिज ऊर्जा 10 Hz की आवृत्ति दोलित होती है । दोलक एक चरम स्थिति से दूसरी स्थिति तक कि समय लेगा? \( \begin{array}{llll}\text { (1) } 0.1 \mathrm{~s} & \text { (2) } 0.2 \mathrm{~s} & \text { (3) } 0.4 \mathrm{~s} & \text { (4) } 0.5 \mathrm{~s}\end{array} \)

3) One of the following is not a source of magnetostatic fields: A dc current in a wire An electric field linearly changing with time A permanent magnet A charged disk rotating at uniform speed

7. माध्यावस्था पर सरल आवर्ती दोलनक की स्थितिज ऊर्जा 20 J है ओ चरम स्थिति पर 100 J है । तो माध्य स्थिति पर गतिज ऊर्जा है- \( \begin{array}{llll}\text { (1) } 120 \mathrm{~J} & \text { (2) } 100 \mathrm{~J} & \text { (3) } 80 \mathrm{~J} & \text { (4) } 20 \mathrm{~J}\end{array} \)