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Question: The height \(y\) and the distance \(x\) along the horizontal plane of a projectile on a certain plan...

The height yy and the distance xx along the horizontal plane of a projectile on a certain planet (with no surrounding atmosphere) are given by y=(8t5t2)y = (8t - 5t^{2}) meter and x=6tx = 6t meter, where tt is in second. The velocity with which the projectile is projected is

A

8 m/sec

B

6 m/sec

C

10 m/sec

D

Not obtainable from the data

Answer

10 m/sec

Explanation

Solution

vy=dydt=810tv_{y} = \frac{dy}{dt} = 8 - 10t, vx=dxdt=6v_{x} = \frac{dx}{dt} = 6

at the time of projection i.e. vy=dydt=8v_{y} = \frac{dy}{dt} = 8and vx=6v_{x} = 6

v=vx2+vy2=62+82=106mum/s\therefore v = \sqrt{v_{x}^{2} + v_{y}^{2}} = \sqrt{6^{2} + 8^{2}} = 10\mspace{6mu} m ⥂ / ⥂ s