Question

1) Which of the following explains why a bicycle uses a gear?

A.)The gear increases the effort force needed.
B.)The gear increases resistance force.
C.)The gear decreases effort force.
D.)The gear decreases resistance force.

2) Which of the following is a compound machine?

A.)a screw being screwed into a piece of wood
B.)a can opener
C.)a crowbar
D.)a wheel and axle

Answer 1

1) D. The gear decreases resistance force

2) B. A car opener

Step-by-step explanation:

1): A bicycle uses a gear to decrease the resistance force as when the gears are shifted, the chain moves from a larger ring to a smaller one thus reducing the surface area of the ring as well as friction which results into a greater speed by applying same amount of effort.

2): As a compound machine is a combination of more than one simple machine. Out of all the options, a car opener is said to be a compound machine as it consist of a lever, screw, wedge and axle and wheel.

These are some of the simple machines which combines to make a complex machine ( car opener ).

Answer 2

1. "The gear decreases effort force" is the one among the following choices given in the question that explains why a bicycle uses a gear. The correct option among all the options is option "C".

2. A can opener is a compound machine. The correct option among all the options that are given in the question is the second option or option "B".