With your left hand grasp something with weight such as a heavy textbook or pencil pouch and hold it at your side. Place your right hand on your upper left arm so that you can feel your muscles move. Slowly bend your left arm to raise the weight. Then slowly straighten your left arm to lower it. Repeat this motion a few times until you can feel and see what is happening. 17. What joint did you use to lift the weight

so easy. just google the electromagnetic waves and it’ll pop up.

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.

the components of a vector are the parts of the vectors that are to each other.

b perpendicular

3. dark matter

empty space could also be a simple vacuum