A body of mass 1kg is projected at an angle 30∘ with horizontal on a level ground at a speed 50m/s. The magnitude of change in momentum of the body during its flight is (g=10m/s2)
A
50kgms−1
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B
100kgms−1
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C
25kgms−1
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D
Zero
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Solution
The correct option is A50kgms−1
We know that in a horizontal plane, Initial velocity of projectile = Final velocity of projectile →pi=mucosθ^i+musinθ^j→pf=mucosθ^i−musinθ^j|−→Δp|=|→pf−→pi|=2musinθ =2×1×50×12=50kgms−1 Alternate Solution:
In the horizontal direction, momentum p doesn’t change. Δpx=0
In vertical direction, Δpy=musinθ−(−musinθ)=2musinθ =2×1×50×12=50kgms−1