Question

A body is projected horizontally with 10 m/s from the top of a tower of height 20m on reaching the ground its displacement is (g=10m/s)
1) 40m
2) 20m
3) 20 rout 2m
4) 40 rout 2 m
​

Answer 1

Given :

Initial velocity = 10m/s

Height of the tower = 20m

To Find :

Displacement of the body.

Solution :

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❖ First of all we need to find time taken by body to reach at the ground.

• Vertical component of velocity is responsible for downward motion.
• Vertical component of initial velocity = zero

➙ h = 1/2 gt²

➙ 20 = 1/2 (10)t²

➙ 20 × 2 = 10t²

➙ t² = 40/10

➙ t = √4

➙ t = 2s

❖ Horizontal distance covered by body :

• Horizontal component of velocity is responsible for motion in forward direction.

➙ R = u × t

➙ R = 10 × 2

➙ R = 20 m

❖ Calculation of displacement :

As per pythagoras theorem,

➠ d² = R² + h²

➠ d² = 20² + 20²

➠ d² = 2(20)²

➠ d = 20√2 m

∴ (3) is the correct answer!

Answer 2

Given :

Initial velocity = 10m/s

Height of the tower = 20m

To Find :

Displacement of the body.

Solution :

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❖ First of all we need to find time taken by body to reach at the ground.

Vertical component of velocity is responsible for downward motion.

Vertical component of initial velocity = zero

➙ h = 1/2 gt²

➙ 20 = 1/2 (10)t²

➙ 20 × 2 = 10t²

➙ t² = 40/10

➙ t = √4

➙ t = 2s

❖ Horizontal distance covered by body :

Horizontal component of velocity is responsible for motion in forward direction.

➙ R = u × t

➙ R = 10 × 2

➙ R = 20 m

❖ Calculation of displacement :

As per pythagoras theorem,

➠ d² = R² + h²

➠ d² = 20² + 20²

➠ d² = 2(20)²

➠ d = 20√2 m

∴ (3) is the correct answer!