PHYSICS

Class:11 P.S. #4


Q.1 Temperature of a body varies with time as T = (T0 + at2 + b sint)K, where T0 is the temperature in Kelvin at t = 0 sec. & a = 2/p. K/s2 & b = - 4 K, then rate of change of temperature at t = psec. is [3]

(A) 8 K (B) 80K (C) 8K/sec (D) 80K/sec

Paragraph for question nos. 2 to 4

In a one dimensional motion position 'x' and time 't' are related as,

(where x is in metres and t is in seconds.)

Q.2 The position of the particle when it's velocity is, 2 m/s, is [3]

(A) 1m (B) 2m (C) 3m (D) None of these

Q.3 Speed of the particle after 6 seconds is [3]

(A) 4 m/s (B) 2 m/s (C) 6 m/s (D) 8 m/s

Q.4 Velocity - time graph is [3]

(A) (B) (C) (D)

[Q.5 has more than one correct option.]

Q.5 A body starts from the origin and moves along the x-axis such that position at any instant is given by , where t is in second and position is in m. Choose the correct options" [4]

(A) At t = 2 sec, the particle is at its local maximum position

(B) At t = 1 sec, the particle is at its local minimum position

(C) At t = 2 sec, the particle is at its local minimum position

(D) At t = 1 sec, the particle is at its local maximum position

Q.6 Column I Column II [6]

(A) (P) Initial acceleration of A is in +ve x direction.

(B) (Q) Initial acceleration of A is zero.

(C) A body A has position given by (R) Speed of A continously increases with time

x = t2 - 3t + 2

(D) (S) Speed of A decreases and then increases with

time.

(T) Initial acceleration of A is in -ve x direction.

Q.7 A rocket rises vertically up from the surface of earth so that it's distance from the earth's surface is l = ct2 where c is a constant. After 10 sec. the rocket has travelled 2 km. Determine it's speed (in m/s) at that moment. [5]

Q.8 A body starts from origin and moves along x axis such that at any instant velocity is vt = 4t3 - 2t where t is in second and vt is in m/s. Find the acceleration of the particle (in m/s2) when it is 2 m from the origin. [5]

Q.9 The x and y component of a particle in the x-y plane at any instant are given by x=at2 and y=2at where a is a constant. The magnitude of velocity of the particle at any instant is given by [3]

(A) (B) (C) (D)

Q.10 A motor boat of mass m moves along a lake with velocity V0. At t = 0, the engine of the boat is shut down. Magnitude of resistance force offered to the boat is equal to rV. (V is instantaneous speed). What is the total distance covererd till it stops completely? [Hint : F(x) = mV = - rV] [3]

(A) mV0/r (B) 3 mV0/2r (C)mV0/2r (D) 2 mV0/r

Q.11 The acceleration of a particle is given by ms_2

At t = 0, = 0 and ms_1. The position vector at t = 2 s is [3]

(A) m (B) m (C) m (D) m

Paragraph for question nos. 12 to 15

In physics, yank is the derivative of force with respect to time. Expressed as an equation, yank Y is :

where F is force and is the derivative with respect to time t.

Y =

where m is mass and v is velocity. If the mass is not changing over time (i.e. it's constant), then :

which can also be written as :

Y = mj

where j is jerk.

Q.12 What are the units of yank ? [3]

(i) kg • m/s3 (ii) (N/s) (iii) N/m (iv) kg m2/s3 (v) kg • m/s2

(A) (i), (ii), (iii), (iv), (v) (B) (i), (ii)

(C) (i), (iii) (D) (ii), (iv)

Q.13 The above parra defines jerk as [3]

(A) Rate of change of velocity (B) Rate of change of acceleration

(C) Rate of change of Yank (D) Rate of change of momentum

Q.14 If the force acting on a body is given by F = 100 - t2, at what time is the yank zero ? [3]

(A) at the initial moment (t = 0) (B) at t = 10 sec

(C) at t = 50 sec. (D) at t = 5 sec.

Q.15 A small squirrel is climbing on a straight vertical pole with a uniform speed of 0.75 m/s. A point observer is located 10m away from base of pole. Find the rate (in cm/s) at which the length of line joining observer and squirrel is changing at t = 10 s. The squirrel is initially (at t = 0) on ground. [5]



ANSWER-KEY


1 C

2 A

3 C

4 C

5 CD

6 (A) Q (B) RT (C) PS (D) ST

7 400

8 22

9 B

10 A

11 B

12 B

13 B

14 A

15 45

Page #