A model rocket is launched straight upward with an initial speed of 47.9 m/s. It

Question

A model rocket is launched straight upward with an initial speed of 47.9 m/s. It accelerate. with a constant upward acceleration of 2.24 m/s^2 until its engines stop at an altitude of 150 m. What is the maximum height reached by the rocket? The acceleration of gravity is 9.81 m/s^2. Answer in units of m. When does the rocket reach maximum height? Answer in units of s. How long is the rocket in the air? Answer in units of s. In order to qualify for the finals in a racing event, a race car must achieve an average speed of 277 km/h on a track with a total length of 1850 m. If a particular car covers the first half of the track at an average speed of 207 km/h, what minimum average speed must it have in the second half of the event in order to qualify? Answer in units of km/h.

Explanation / Answer

Q39)

by Newton's Law of Motion-

v^2=u^-2gh

Here , v=0, u=47.9 m/s,h=?

0=(47.9)^2-2x9.8xh

h=117.06 m

Ans- Maximum height is 117.06m

Q40)

By first Law-

v=u-g.t

0=47.9-9.8t

t=4.88 sec

Ans- Rocket will reach maximum height in 4.88 sec

Q41)

By third Law,

h=ut-0.5gt^2

117.06=47.9t-0.5x9.8t^2

117.06=47.9t-4.9t^2

47.9t-4.9t^2-117.06=0

4.9t^2-47.9t+117.06=0

t=

Q42)

Av Speed=2a.b/a+b

277=2x207xb/(207+b)

277=414b(207+b)

0.669=207b+b^2

b^2+207b-0.669=0

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