A particle is projected vertically upwards with a speed of 40 m/s. At what times...
FURTHER MATHEMATICS
WAEC 2007
A particle is projected vertically upwards with a speed of 40 m/s. At what times will it be 35m above its point of projection? \(\text{Take g} = 10 ms^{-2}\)
- A. 1 sec and 7 sec
- B. 1 sec and 8 sec
- C. 2 sec and 5 sec
- D. 2 sec and 7 sec
Correct Answer: A. 1 sec and 7 sec
Explanation
\(s = ut + \frac{1}{2}at^{2}\)
\(s = ut - \frac{1}{2}gt^{2}\) (Upward movement against gravity)
\(35 = 40t - \frac{1}{2}10t^{2}\)
\(35 = 40t - 5t^{2}\)
\(5t^{2} - 40t + 35 = 0\)
\(t^{2} - 8t + 7 = 0\)
\((t - 1)(t - 7) = 0 \implies t = \text{1 sec and 7 sec}\)
Post an Explanation Or Report an Error
If you see any wrong question or answer, please leave a comment below and we'll take a look. If you doubt why the selected answer is correct or need additional more details? Please drop a comment or Contact us directly. Your email address will not be published. Required fields are marked *