1. Compute the momentum of each of the following situations. a. A 0.27 kg baseba

Question

1.     Compute the momentum of each of the following situations.

a.      A 0.27 kg baseball moving toward the batter at a velocity of 13.2 m/s (answer in kg·m/s)

b.     A 77 kg skater traveling at 10 m/s (answer in kg·m/s)

c.      A 90 kg running back moving at 3 m/s (answer in kg·m/s)

d.     A 520 N skier traveling at 15 m/s (answer in kg·m/s)

e.      A 200 lb student moving at 3 ft/s (answer in slug·ft/s)

2.     After a 70 kg high jumper goes over 2 meter bar, his body collides with the mat in a 0.01 seconds.   How much force is exerted by the high jumper?  

3.     Compute the amount of work done in each of the following situations:

a.      A weight lifter bench presses 150 N upward 80 cm

b.     A rugby player runs 50 m while carrying a 450g (0.45kg) ball

4.     Compute the amount of power developed in each of the following situation

a.      Jon snatched 100kg. In a snatch, the barbell is moved from a stationary position on the floor to a stationary position over the athlete’s head. Only 0.5 sec elapsed from the first movement of the barbell until it was overhead, and the barbell moved through a vertical displacement of 2.0 m. What was Jon’s average power output?

b.     A soft ball player lifts a 16 oz. softball 6.5 feet in 0.4 sec. What is the power developed?

5.     Compute the amount of kinetic energy developed in each of the following situations: (1 foot·lb = 1.3558 J)

a.      A 154 lb athlete is sprinting at a rate of 24 ft/sec (answer in J)

b.     A 160 pound diver jumps from a 20 m platform. How much kinetic energy will he have developed after falling for 1 sec (answer in J)? How much after falling 1.5 sec (answer in J)?

6.     How much kinetic energy is developed by a 700 N pole vaulter that falls from a height of 4 meters?

7.     A football player pushes a 670N blocking sled. The coefficient of static friction between sled and grass is 0.73, and the coefficient of dynamic friction between sled and grass is 0.68.

a.      How much force must the player exert to start the sled in motion?

b.     How much force is required to keep the sled in motion?

c.      Answer the same two questions with a 100 kg coach standing on the back of the sled.

  8.       A 981N rugby player traveling with a velocity of 7 m/s collides head-on with an 882.9 N player traveling at 8 m/s. What is their combined velocity (in which direction)?

9. A 65 kg diver is positioned so that his radius of gyration is 0.6 m as he leaves the board with an angular velocity of 258°/s. What is the diver’s angular velocity when he assumes a tuck position, altering his radius of gyration to 0.20 m?

10. If a diver has an angular momentum of 30 kgm2/s and has an angular velocity of 20 degrees per sec, what would his moment of inertia be?

Explanation / Answer

Q.1 (a) p = mv = 0.27 ( 13.2) = 3.564 KG M/S

b) p = 77 (10) = 770 kg m/s

c) P= 90 ( 3) = 270 kg m/s

d) P = W/g ( v) = (520)/9.8 (15) = 795. 912 kg m/s

e)200 lb = 6.21619 slug

p = 6.21619 ( 3 ) = 18.648 slug f/sec

Q.2 velcity of jumper = sqrrot ( 2gh) = sqroot( 2 x 2 x 9.8) = 6.26 m/s apprx

force = mv / t = 70 ( 6.26)/ 0.01 = 43826.9 N apprx

Q. 3) a) work done = 150 ( 0.8) = 120 J

b) 0 J ( no work is done because displacement and fiorce are perpendicular to each other)

Q. 4

a ) power = work done/ time= 100kg ( 2m) 9.8/0.5 = 3920 watts

b)16 oz= 0.453592 kg

6.5 feet = 1.9812 m

power = 0.453592 ( 1.9812) ( 9.8) /0.4 = 22.017 watts

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