# What is the acceleration of the baseball?

16. A batter strikes a baseball of mass 0.15 kg with a force of 18 kN. What is the acceleration of the baseball?

(Points : 3)

9.8 m/s2

120,000 m/s2

2,700 m/s2

8.3 m/s2

17. A block of metal weighs 60 newtons on the earth. You take it to the moon and find it weighs 10 newtons. With what acceleration will it fall on the moon?

(Points : 3)

6.0 m/s2

1.6 m/s2

9.8 m/s2

1.0 m/s2

18. A 60 kg student in a rowboat on a still lake decides to dive off the back of the boat. The student's horizontal acceleration is 2.0 m/s2 while in contact with the boat. What horizontal force does the student exert on the boat?

(Points : 3)

30 N toward the front of the boat

30 N toward the back of the boat

120 N toward the back of the boat

120 N toward the front of the boat

19. A pitcher exerts a force on a baseball that is 30 times the ball's weight. How fast is the pitcher accelerating the ball?

(Points : 3)

290 m/s2

1.0 m/s2

9.8 m/s2

30 m/s2

20. A dog that is soaking wet will typically shake its body rapidly to remove water from its fur. Which of the following is the best explanation for this?

(Points : 3)

The force of shaking back and forth is the action, and the force pushing the water from the dog's fur is the reaction.

The water droplets are small and require zero force to accelerate them.

After leaving the dog's hair, the water tends to continue moving in the same direction when the fur's motion changes direction.

The mass of the dog is smaller than the inertia of the water.

• 16

a = 18e3/ 0.15 = 120,000 m/s2

17

m = 60 /10 = 6 kg

g’ at moon = 10 /6 = 1.6 m/s²

18

120 N toward the front of the boat

19

30 times the ball's weight => 30times g = 290 m/s²

20

After leaving the dog's hair, the water tends to continue moving in the same direction when the fur's motion changes direction.

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