Force = mass * acceleration Force = (4kg + 46kg) * 3 m/s2 Force = 50kg * 3 m/s2 Force = 150 kg*m/s2 or Force = 150 Newtons
What is the acceleration of a runner whose mass is 50 kg if the runner is being pushed along by a force of 100 newtons?
does not accelerate
He, along with his contemporaries, laid the foundations for modern science.
In order to accelerate 70 kg at 2 m/s2, 140 newtons of net force must act on the mass in the direction of the acceleration. We don't usually think of the accelerating force on a bicycle as coming from the road, although I guess there's not many other choices. The forces at the place where the road meets the bicycle are complicated. Don't forget about the upward force that the road exerts on the bicycle, equal to the bicycle's weight. That force is there too.
The next best "sensation" of rolling along smoothly with a skateboard, was using roller skates. For years, roller skating rinks were very popular places for fun and amusement.
If the speed of sliding along the table is constant, then there's no acceleration, and the 'net' force on the mass and anywhere along the connection to the scale is zero. At the point where the hook of the scale engages the mass, there is no acceleration. The mass is pulling the hook backwards with a force of 20 newtons, and somebody's finger is pulling the spring scale forward with a force of 20 newtons. The mass or weight of the object sliding along on the table is irrelevant.