Physics-DPP-3-work, power and energy

PHYSICS Topic: WORK, POWER AND ENERGY Date: 1. A particle suspended by a light inextensible thread of length l is projected horizontally from its lowest position with velocity . The string will slack after swinging through an angle equal to : (a) 30o (b) 90o (c) 120o (d) 150o 2. System shown in figure is released from rest. Pulley and spring is massless and friction is absent everywhere. The speed of 5 kg block when 2 kg block leaves the contact with ground is : (Take force constant of spring k = 40 N/m and g = 10 m/s2) (b) 2 2 m / s (c) 2 m / s (d) 4 2 m / s 3. A particle moves from rest at A on the surface of a smooth circular cylinder of radius r as shown. At B it leaves the cylinder. The equation relating α and β is (a) 3 sin α = 2 cosβ (b) 2 sin α = 3 cosβ (c) 3 sinβ = 2 cosα (d) 2 sinβ = 3 cosα 4. A uniform flexible chain of mass m and length l hangs in equilibrium over a smooth horizontal pin of negligible diameter. One end of the chain is given a small vertical displacement so that the chain slips over the pin. The speed of chain when it leaves pin is : (a) (b) (c) (d) 5. The area of the acceleration displacement curve of a body gives : (a) impulse (b) change in momentum per unit mass (c) change in KE per unit mass (d) total change in energy PHYSICS Topic: WORK, POWER AND ENERGY Date: 6. A mass spring system oscillates such that the moves on a rough surface have coefficient of friction μ . It is compressed by a distance a from its normal length and, on being released, it moves to a distance b from its equilibrium position. The decrease in amplitude for one half-cycle (– a to b) is : (a) μmg K (b) 2μmg K μg (c) K (d) K μmg 7. A small body of mass m slides without friction from the top of a hemisphere of radius r. At what height will be body be detached from the centre of the hemisphere ? (a) h = r 2 (b) h = r 3 (c) h = 2r 3 (d) h = r 4 8. The potential energy between the atoms in a molecule is given by : U(x)= a - b x12 x6 where a and b are positive constants and x is the distance between the atoms. The atom is in stable equilibrium when : æa ö1/ 6 æ2a ö1/6 æ11a ö1/6 (a) x = 0 (b) x = ç ÷ (c) x = ç ÷ (d) x = ç ÷ çè2bø÷ çè b ø÷ çè 5b ø÷ 9. A stone is thrown at an angle of 45o to the horizontal with kinetic energy K. The kinetic energy at the highest point is : K (a) 2 (b) (c) K (d) zero 10. The relationship between the force F and position x of a body is as shown in figure. The work done in displacing the body from x = 1 m to x = 5 m will be : (a) 30 J (b) 15 J (c) 25 J (d) 20 J PHYSICS Topic: WORK, POWER AND ENERGY Date: Answer Key 1. (c) 2. (b) 3. (c) 4. (a) 5. (a ) 6. (b) 7. (c) 8. (c) 9. (a) 10. (b)