My Physics Guide

Chapter–2 Units and Measurements Qn 1. Check whether the relation  mv 2  = mgh is dimensionally correct or not. Here v = speed, m = mass, g = acceleration and h = height Qn 2. convert the unit: 6.67 × 10 –11 N m 2 (kg) –2 = ........... (cm) 3 s –2 g –1 . Qn 3. Write the dimensional formula of these physical quantities:  electric potential V, resistance, pressure, power, density, universal constant of gravitation and potential energy. Qn 4. Consider a simple pendulum, having a bob attached to a string, that oscillates under the action of the force of gravity. Suppose that the period of oscillation of the simple pendulum depends on its length  (l), mass of the bob (m) and acceleration due to gravity (g). Derive the expression for its time period using the method of dimensions. Qn5. The centripetal force ‘F’ may depend upon the radius ‘r’ of the circle, mass ‘m’ and speed ‘v’ of the particle. Derive the expression for the Force F, using the method of dimensions....

  Impulse: We sometimes encounter examples where a large force acts for a very short duration producing a finite change in momentum of the body. The product of this  force and time is called impulse. Impulse = Force × time duration = Change in momentum The force is called an impulsive force. Example 5.4   A batsman hits back a ball straight in the direction of the bowler without changing its initial speed of 12 m s –1 . If the mass of the ball is 0.15 kg, determine the impulse imparted to the ball. (Assume linear motion of the ball) Answer: Change in momentum = 0.15 × 12–(–0.15×12) = 3.6 N s, Impulse = 3.6 N s, in the direction from the batsman to the bowler. Equilibrium of a particle: Equilibrium of a particle is the situation when the net external force on the particle is zero. Equilibrium under three concurrent forces F1, F2 and F3 requires that the vector sum of the three forces is zero. F1 + F2 + F3 = 0 Example 5.6  A mass of 6 kg is suspended by a rope of lengt...