UNIT TEST- Class 11 Physics

The speed of a swimmer in still water is 20 m/s. The speed of river water is 10 m/s and is flowing due east. If he is standing on the south bank and wishes to cross the river along the shortest path the angle at which he should make his strokes w.r.t. north is given by :

• 30° west

• 0°

• 60° west

• 45° west

Two particles A and B are moving in uniform circular motion in concentric circles of radii  $r_A$   and  $r_B$ with speed  $v_A$   and  $v_B$   respectively. Their time period of rotation is the same. The ratio of angular speed of A to that of B will be :

•  $r_A\ :\ r_B$  

• 1:1

•  $v_A:\ v_B$  

•  $r_B\ :\ r_A$  

When an object is shot from the bottom of a long smooth inclined plane kept at an angle 60° with horizontal, it can travel a distance  $x_1$    along the plane. But when the inclination is decreased to 30° and the same object is shot
with the same velocity, it can travel  $x_2$   distance. Then  $x_1:\ x_2$   will be:

•  $1:\sqrt{2}$  

•  $\sqrt{2}:\ 1$  

•  $1:\ \sqrt{3}$  

•  $1\ :\ 2\sqrt{3}$  

In an experiment, the percentage of error occurred in the measurement of physical quantities A, B, C and D are 1%, 2%, 3% and 4% respectively. Then the maximum percentage of error in the measurement X, where X =  $\frac{A^2\ \sqrt{B}}{\sqrt{C}\ D^3}$ will be

• (3/13) %

• 16.5 %

• -10 %

• 10 %

The angle between  $\overrightarrow{A}$   =   $i^`\ +j^`$  and between   $\overrightarrow{B\ }$  =   $i^`\ -j`$    is 

•  $45^0$  

•  $120^0$  

•  $30^0$  

•  $90^0$  

A block of mass 2 kg rests on a rough inclined plane making an angle of 30° with the horizontal. The co-efficient of static friction between the block and the plane is 0.7. The frictional force on the block is

• 9.8 N

• $\sqrt{3}$ 9.8 N

• 0.7 x 9.8 N

• None of the above

In the arrangement, shown in the figure, the ends P and Q of an un-stretchable string move downwards with uniform speed u. Pulleys A and B are fixed. Mass M moves upwards with a speed -

• $2u\cos\theta$

• $\frac{2u}{\cos\theta}$

• $\frac{u}{\cos\theta}$

• $u\cos\theta$

The pulleys and the strings shown in the figure are smooth and of negligible mass. For the system to remain in equilibrium, the angle  $\Theta$   should be

• $0^0$

• $30^0$

• $45^0$

• $60^0$

What is the maximum value of the force F such that the block shown in the arrangement, does not move ? (g =  $10\ ms^{-2}$ )

• 20 N

• 10 N

• 15 N

• 25 N

In 1.0 sec. a particle goes from point A to point B, moving in a semicircle of radius 1.0 m as shown in the figure. The magnitude of the average velocity is :

• 3.14 m/s

• 2 m/s

• 1 m/s

• 0