A plane lands with a velocity of +125.3 m/s and decelerates at a maximum rate of

Question

A plane lands with a velocity of +125.3 m/s and decelerates at a maximum rate of 6.2 m/s^2. From the instant the plane touches the runway, what is the minimum time needed before it can come to rest? Answer in units of s. The plane is landing on a naval aircraft carrier that is 0.80 km long. What distance does the plane require to land? Answer in units of km. A car starts from rest and travels for 6.5 s with a uniform acceleration of +1.8 m/s2. The driver then applies the brakes, causing a uniform deceleration of 1.5 m/s2. If the brakes are applied for 2.1 s, how fast is the car going at the end of the braking period? Answer in units of m/s. How far has it gone from its start? Answer in units of in.

Explanation / Answer

1) v = u + at

0 = 125.3 - 6.2t

t = 125.3 / 6.2

t = 20.21 m/s

b) v^2 = u^2 + 2aS

S = 125.3^2 / 2*6.2 = 1266.136 m = 1.27 km

distance need = 1.27 - 0.80 = 0.47 km

2) v1 = u + at

v! = 6.5*1.8 = 11.7 m/s

V final = 11.7 - 1.5*2.1 = 8.55 m/s

b) S1 = at^2 / 2 = 1.8*6.5^2 / 2 = 38.025 m

S2 = 11.7*2.1 - 1.5*2.1^2 / 2 = 21.262 m

Total distance covered = S1 + S2 = 59.29 m

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