Question

can u give the solution​

Answer 1

Answer : option (2) 180m/s

explanation : we know, area enclosed by thrust - time graph = change in linear momentum.

or, area of trapezium as shown in figure = m(v - u)

but rocket starts from rest so, u = 0

or, area of trapezium = mv .......(1)

and area of trapezium = 1/2 × (sum of parallel side) × distance between two parallel side

= 1/2 × (30s + 60s) × 4000N

= 180000 Ns......(2)

given, weight of rocket , m = 1ton = 1000kg

now from equations (1) and (2),

180000 Ns = 1000 × v

v = 180 m/s

hence, velocity of rocket after 1 minute is 180 m/s .