The horizontal velocity of an athlete\'s hip after it passed over a hurdle was v

Question

The horizontal velocity of an athlete's hip after it passed over a hurdle was vh = 5.8 m/s. At the instant immediately before the hurdler's foot landed on the ground, her leg was straight and vertical, and it was rotating backward at the hip joint with an angular velocity = 380º/s. If the length of the leg (from the hip joint to the foot) was d = 0.91 m, what is the horizontal linear velocity of the foot relative to the ground? Hints: If the foot was moving forward relative to the ground, you should report a positive velocity value; otherwise, a negative velocity value. You first need to figure out the linear velocity of the foot relative to the hip. Then, knowing the linear velocity of the hip relative to the ground and the linear velocity of the foot relative to the hip, you should be able to figure out the linear velocity of the foot relative to the ground.

Explanation / Answer

Angular velocity = 2x3.14x380/360 = 6.63 rad/sec

Since the foot is going backward at hip joint, so linear velocity of foot with respect to hip will be opposite in the direction of forward motion. This value is = Angular velocity x radius = 6.63 x 0.91 = 6.03 m/s

Hips foward linear velocity = 5.8 m/s

So horizontal linear velocity of the foot relative to the ground = 5.8 - 6.03 = -0.23 m/s

So net horizontal linear velocity of the foot relative to the ground will be in backward direction of motion.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.