Question

A young girl is riding a bicycle that has a total mass (including the kid) of 20.1 kg. the girl is moving at 5.1 m/s on a flat road when she suddenly slams on the brakes and skids to a stop in 13.1 meters. how many joules of work was done on the bike girl?

Answer 1

The work done on the bike and girl by friction as she comes to a stop is -259.5305 joules, indicating that this amount of energy is removed from the system.

Step-by-step explanation:

To calculate the work done on the bike and the girl as she comes to a stop, we can use the work-energy principle. The work done by the friction force is equal to the change in kinetic energy of the girl and her bicycle. Since she comes to a stop, her final kinetic energy is 0, and the initial kinetic energy can be calculated using the equation KE = (1/2)mv2, where m is the mass and v is the velocity.

The initial kinetic energy is:

KEi = (1/2) * 20.1 kg * (5.1 m/s)2 = 259.5305 J

The final kinetic energy is 0 J since the girl stops completely:

KEf = 0 J

The work done by friction, which brings the bike and the girl to a stop, is equal to the negative change in kinetic energy:

Work = KEf - KEi = 0 J - 259.5305 J = -259.5305 J

Therefore, the work done on the bike and girl by friction is -259.5305 joules, which indicates that energy is removed from the system by friction.