Question

While launching a rocket of mass 2×10^4 kg, a force of 5×10^5 N is applied for 20s. Calculate the velocity attained by the rockets at the end of 20s.

(a) 3.6m/s

(b) 300m/s

(c) 120m/s

(d) 500m/s

The question was posed to me by my college director while I was bunking the class.

Asked question is from Gravity topic in portion Laws of Motion of Engineering Physics I

Answer 1

The correct option is (d) 500m/s

To explain: m = 2×10^4kg F = 5×10^5N  t = 20s u = 0 v = ?

Impulse of force = F×t = m(v-u)

5×10^5×20 = 2×10^4(v-0)

v = 500m/s.