Introduction to 2D Motion

Q. Which of the following represents a 2D motion?

1. A ball thrown vertically upwards
2. Motion of a pendulum
3. A stone dropped from a cliff
4. All of these

Q. A person standing on open ground hears the sound of a jet airplane, coming from the north at an angle ${30}^{\circ }$ with the horizontal. But he finds the airplane vertically above his position. If $v$ is the speed of sound, then speed of the plane is

1. $\frac{\sqrt{3}}{2}v$
2. $v$
3. $\frac{2}{\sqrt{3}}v$
4. $\frac{v}{2}$

Q. A person standing on open ground hears the sound of a jet airplane, coming from the north at an angle ${30}^{\circ }$ with the horizontal. But he finds the airplane vertically above his position. If $v$ is the speed of sound, then speed of the plane is

1. $\frac{\sqrt{3}}{2}v$
2. $v$
3. $\frac{2}{\sqrt{3}}v$
4. $\frac{v}{2}$

Q. A man wishes to cross a river and come back to original position by swimming minimum distance. If the width of the river is 50 m, speed of river is 2 m/s and velocity of man with respect to river is 4 m/s, then time taken by man to come back to original position is

1. 
   $\frac{50}{\sqrt{3}}$ sec
2. 
   50$\sqrt{2}$ sec
3. 
   25 sec
4. 
   25$\sqrt{3}$ sec

Q. A person standing on open ground hears the sound of a jet airplane, coming from the north at an angle ${30}^{\circ }$ with the horizontal. But he finds the airplane vertically above his position. If $v$ is the speed of sound, then speed of the plane is

1. $\frac{\sqrt{3}}{2}v$
2. $v$
3. $\frac{2}{\sqrt{3}}v$
4. $\frac{v}{2}$

Q. A man wishes to cross a river and come back to original position by swimming minimum distance. If the width of the river is 50 m, speed of river is 2 m/s and velocity of man with respect to river is 4 m/s, then time taken by man to come back to original position is

1. 
   $\frac{50}{\sqrt{3}}$ sec
2. 
   50$\sqrt{2}$ sec
3. 
   25 sec
4. 
   25$\sqrt{3}$ sec