11. a student lifts a 25 kg mass a vertical distance of 1.6 m in a time of 2.0 seconds.
a. find the force needed to lift the mass (in n).
b. find the work done by the student (in j).
c. find the power exerted by the student (in w).

a) 245 N

b) 392 J

c) 196 W

Explanation:

a) Force needed to lift the 25 kg object is the same as the weight of the object:

b) Work is the force exerted times the distance moved:

c) The power exerted is the quotient of the work done over the amount of time it took to move the object:

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.