#### Kinematics Book Back Questions

11th Standard

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Physics

Time : 00:45:00 Hrs
Total Marks : 30
5 x 1 = 5
1. Two objects of masses m1 and m2 fall from the heights h1 and h2 respectively. The ratio of the magnitude of their momenta when they hit the ground is

(a)

$\sqrt { \frac { { h }_{ 1 } }{ { h }_{ 2 } } }$

(b)

$\sqrt { \frac { { { m }_{ 1 }h }_{ 1 } }{ { { m }_{ 2 }h }_{ 2 } } }$

(c)

$\frac { { m }_{ 1 } }{ { m }_{ 2 } } \sqrt { \frac { { h }_{ 1 } }{ { h }_{ 2 } } }$

(d)

$\frac { { m }_{ 1 } }{ { m }_{ 2 } }$

2. If an object is dropped from the top of a building and it reaches the ground at t = 4 s, then the height of the building is (ignoring air resistance) (g = 9.8 ms-2)

(a)

77.3 m

(b)

78.4 m

(c)

80.5 m

(d)

79.2 m

3. If a particle executes uniform circular motion, choose the correct statement

(a)

The velocity and speed are constant

(b)

The acceleration and speed are constant.

(c)

The velocity and acceleration are constant.

(d)

The speed and magnitude of acceleration are constant.

4. Two objects are projected at angles 30° and 60° respectively with respect to the horizontal direction. The range of two objects are denoted as R30° and R60° Choose the correct relation from the following.

(a)

R30° =R6 ​​​​​​​

(b)

R30° =4R6

(c)

R30° =$\frac{R_{60°}}{2}$

(d)

R30° =2R6

5. An object is dropped in an unknown planet from height 50 m, it reaches the ground in 2 s . The acceleration due to gravity in this unknown planet is

(a)

g=20 ms-2

(b)

g=25 ms-2

(c)

g=15 ms-2

(d)

g=30 ms-2

6. 4 x 2 = 8
7. A particle has its position moved from $\overset { \rightarrow }{ { r }_{ 1 } } =3\hat { i } +4\hat { j }$ to $\overset { \rightarrow }{ { r }_{ 2 } } =\hat { i } +2\hat { j }$ Calculate the displacement vector ($\Delta$$\overrightarrow { r }$) and draw the $\overrightarrow { { r }_{ 1 } }$, $\overrightarrow { { r }_{ 2 } }$ and $\Delta \overrightarrow { r }$  vector in a two dimensional cartesian coordinate system.

8. A particle is projected at an angle of 6 with respect to the horizontal direction. Match the following for the above motion.
(a) vx - decreases and increases
(b) vy - remains constant
(c) Acceleration - varies
(d) Position vector - remains downward

9. Two vectors are given as $\vec r=2\hat i+3\hat j+5\hat k$ and $\vec F=3\hat i-2\hat j+4\hat k$ Find the resultant vector $\vec { \tau } =\vec { r } \times \vec { F }$.

10. A train 100 m long is moving with a speed of 60 km h-1. In how many seconds will it cross a bridge of 1 km long?

11. 4 x 3 = 12
12. Define acceleration.

13. An athlete covers 3 rounds on a circular track of radius 50 m. Calculate the total distance and displacement travelled by him.

14. The velocity of three particles A, B, C are given below. Which particle travels at the greatest speed?
$\vec {v_A}=3\hat i+5\hat j+2\hat k$
$\vec {V_B}=\hat i+2\hat j+3\hat k$
$\vec{V_C}=5\hat i+3\hat j+4\hat k$

15. A particle moves in a circle of radius 10m. Its linear speed is given by v = 3t where 1is in second and v is in ms-1.
(a) Find the centripetal and tangential acceleration at t = 2 s.
(b) Calculate the angle between the resultant acceleration and the radius vector.

16. 1 x 5 = 5
17. In the cricket game, a batsman strikes the ball such that it moves with the speed 30ms-1 at an angle 30° with the horizontal as shown in the figure. The boundary line of the cricket ground is located at a distance of 75 m from the batsman? Will the ball go for a six? (Neglect the air resistance and take acceleration due to gravity g = 10m s-2).