9

17

For a group of black mussels, all of which have a shell length of 80 millimetres, the difference between the
drop heights required to fracture the mussels when they drop onto rock and wet beach sand is closest to

A

0.6 metres.

C

1.9 metres.

B

1.0 metres.

D

2.5 metres.

18

To fracture a black mussel which has a mass of 30 grams by impact with wet beach sand, the least impact
speed required is nearest to

A

4.5 metres per second.

C

8.4 metres per second.

B

6.8 metres per second.

D

10 metres per second.

19

Which one of the following statements about the relationships between impact speed, drop height, and
shell length of black mussels is supported by the available evidence?

A

For a given impact speed, the drop height is dependent on the shell length.

B

For a given drop height, the impact speed is independent of the shell length.

C

For a given shell length, the impact speed is independent of the drop height.

D

Neither 

A

 nor 

B

 nor 

C

 is supported by the available evidence.