Ian walks 2 km to his best friend's house, then walks 0.5 km to the library. he then makes a 2.5 km walk home. the entire walk took him 3 hours. what is his average speed in km/h?

Ian's average speed in km/h = 1.66

Explanation:

  We know that average speed is the ratio of distance traveled and time taken for that distance to cover.

  In this case Ian walks 2 km to his best friend's house, then walks 0.5 km to the library. He then makes a 2.5 km walk home.

  So total distance traveled = 2+0.5+2.5 = 5 km

  Time taken for this 5 km distance travel = 3 hours

  So average speed = 5/3 =1.66 km/hour

  Ian's average speed in km/h = 1.66

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.