Question

jake pushes a heavy box across a carpeted floor.Name three forces that act on the box, and explain how you know these are unbalenced

Answer 1

Answer:

The forces acting on the heavy box pushed across the carpeted floor are:

- Gravitational force: this force acts on any object with mass, and it always acts downwards (towards the Earth's centre). its magnitude is

$W=mg$

where m is the mass of the box and g is the acceleration due to gravity.

- Normal force: this is the reaction force exerted by the floor on the box, N, and it acts upward, in the direction opposite to gravity. This force perfectly balances the force of gravity along the vertical direction.

- Applied force: this is the force due to the push applied by Jake, $F$. It acts horizontally in the forward direction.

- Force of friction: this is a resistive force that acts in the opposite direction to the motion of the box, $F_f$, and it is due to the contact between the microbumps present on the surface of the box and of the floor.

While the forces along the vertical direction are balanced, the forces along the horizontal direction are not, since the applied force is larger than the frictional force:

$F>F_f$

This means that the net force along the horizontal direction is non-zero:

$F_{net}=F-F_f > 0$

And according to Newton's second law of motion, this also means that the box has a non-zero acceleration along the horizontal direction:

$F_{net}=ma \rightarrow a=\frac{F_{net}}{m}>0$