A mass of 1 kg is thrown up with a velocity of 100 m s⁻¹. After 5 seconds, it explodes into two parts. One part of mass 400 g comes down with a velocity 25 m s⁻¹. The velocity of the other part is (take g=10 m s⁻²)

Question

Accepted Answer

(3) 100 m s⁻¹. Given: 1 kg thrown up at 100 m s⁻¹; after 5 s it splits into 0.4 kg moving down at 25 m s⁻¹ and 0.6 kg. Idea: find the speed just before the explosion, then conserve momentum across it, counting upwards as positive. Speed at 5 s: v=u-gt=100-10×5=50 m s⁻¹ upwards. Momentum before the explosion =1×50=50 kg m s⁻¹. After: 0.4×(-25)+0.6× v'=-10+0.6v'. 50=-10+0.6v', so 0.6v'=60 and v'=100 m s⁻¹ upwards.

A mass of 1 kg is thrown up with a velocity of 100 m s⁻¹. After 5 seconds, it explodes into two parts. One part of mass 400 g comes down with a velocity 25 m s⁻¹. The velocity of the other part is (take g=10 m s⁻²)

Step-by-step solution

Why the other options are wrong