A rocket of mass 4000kg is set for vertical firing. How much gas must be ejected per second so that the rocket may have initial upwards acceleration of magnitude 19.6m/s2? [Exhaust speed of fuel =980m/s]
A
240kg/s
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
80kg/s
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
120kg/s
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D
None
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution
The correct option is C120kg/s For upward motion of rocket, thrust force must be greater in magnitude than its weight and net force will be equal to their difference, i.e.,
Upwardthrust−Weight=Fnet
−vedmdt−mg=ma
−dmdt=ma+mgve
Here, negative sign is implying that mass of gas is decreasing with the passage of time and ve=980m/s is the exhaust speed of fuel.