Assuming constant velocities, if a fastball pitch is thrown and travels at 40 m/s toward home plate, 18 m away, and the head of the bat is simultaneously traveling toward the ball at 18.0 m/s, how much time elapses before the bat hits the ball?
question 9 options:
about 0.3 s
about 0.6 s
about 0.9 s
about 1.2 s

About 0.3 s

Explanation:

First of all, we need to calculate the speed of the bat relative to the ball. This is given by the sum of the speed of the ball and the speed of the bat:

Now, the time elapsed before the bat hits the ball is given by:

where

d = 18 m is the initial distance between the bat and the ball

v = 58.0 m/s is the speed of the bat relative to the ball

Substituting,

So the closest answer is

About 0.3 s

1 a

2 b

3 b

4 d

5 d

6 d

explanation:

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s