NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Physics
- Chapter
- Motion in Two Dimensions
NTA Abhyas 2020 · Physics · Motion in Two Dimensions
A truck is moving with a constant velocity of 54 km/h. In which...
A truck is moving with a constant velocity of 54 km/h. In which direction (angle with the direction of motion of track) should a stone be projected up with a velocity of 20 m/s, from the floor of the truck, so as to appear at right angles to the truck, for a person standing on the earth ?
Options
- A
- B
- C
- D
Correct answer
A.
Step-by-step solution
Let the stone be projected at an angle α to the direction of motion of truck with a speed of v = 20 m/s.
Since the resultant displacement along horizontal is zero.
The velocity along horizontal = 0
1 5 + 2 0 \text\cos \alpha = 0 ⇒ \text\cos \alpha = - \dfrac{3}{4}
$⇒ \alpha = \cos^{-1} \left(- \dfrac{3}{4}\right)
Since the resultant displacement along horizontal is zero.
The velocity along horizontal = 0
1 5 + 2 0 \text\cos \alpha = 0 ⇒ \text\cos \alpha = - \dfrac{3}{4}
$⇒ \alpha = \cos^{-1} \left(- \dfrac{3}{4}\right)