A pebble is thrown vertically upwards with a speed of 20 m `s^(-1)`. How high will it be after 2 s? (Take g = 10 m `s^(-2)`)

Explanation

To solve the problem of how high the pebble will be after 2 seconds when thrown vertically upwards with an initial speed of 20 m/s, we can use the following steps:

### Step-by-Step Solution:

1. **Identify the given values:**
- Initial velocity (u) = 20 m/s (upwards)
- Time (t) = 2 s
- Acceleration due to gravity (g) = -10 m/s² (negative because it acts downwards)
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