Question

a cyclist is travelling at 50 metre per second it applies brakes so that she doesn't collide with the wall 18 away what declaration must she have
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Answer 1

Initial velocity, u = 50 m/s

Final velocity, v = 0 m/s

Distance of the wall, s = 18 m

We need to find the deceleration of the cyclist.

We know,

$\boxed{\tt{\dag\ v^2=u^2+2as}}$

Putting the values :-

$\tt{\dashrightarrow (0)^2=(50)^2+2\times a \times 18}\\\\\tt{\dashrightarrow 0=2500+36a}\\\\\tt{\dashrightarrow 36a=-2500}\\\\\tt{\dashrightarrow a=\dfrac{-2500}{36} }\\\\\boxed{\boxed{\tt{\dashrightarrow a=-144\ m/s^2}}}$

Hence, the cyclist must retar.d with a deceleration of 144 m/s².

Answer 2

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Question :-

▪ A cyclist is travelling at 50 metre per second it applies brakes so that she doesn't collide with the wall 18 away .what declaration must she have ?

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Given :-

• Initial velocity =50m/s

• Final velocity =0m/s

• Distance =18m.

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To Find:-

▪ Declaration

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Solution :-

By using 3rd equation of motion

$v { }^{2} = u {}^{2} + 2as \\ \\ 0 {}^{2} = 50 {}^{2} + 2 \times a \times 18 \\ \\ - 2500 = 36 \times a \\ \\ a = \frac{ - 2500}{36} \\ \\ a = - 69.44ms {}^{ - 2}$

∴ The decleration of she must have 69.44m/s²