<p>A man of 60 kg is running on the road and suddenly jumps into a stationary trolly car of mass 120 kg. Then, the trolly car starts moving with velocity 2 <span class="equation">\(ms^{-1}\)</span>. The velocity of the running man was ___________ <span class="equation">\(ms^{-1}\)</span>​​​​​​​, when he jumps into the car.</p>