A ball is projected with kinetic energy E at an angle of 45∘ to the horizontal. At the highest point during its flight, its kinetic energy will be:
A
Zero
B
E/2
C
E/2
D
E
Step-by-Step Solution
Initial Energy: The initial kinetic energy is given by E=21mv2, where v is the initial speed of projection .
Velocity at Highest Point: In projectile motion, the horizontal component of velocity (vx=vcosθ) remains constant, while the vertical component (vy) becomes zero at the highest point. Thus, the velocity at the highest point is v′=vcos45∘=2v .
Final Energy: The kinetic energy at the highest point is:
E′=21m(v′)2=21m(2v)2=21m(2v2)=21(21mv2).
Conclusion: Substituting E, we get E′=E/2.
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