Exercise 6.5
Repeat steps and for laminated table top while ensuring that the points A, B and C are marked at the same distances as earlier. Does the stack of coins travel a larger distance than it did on the wooden table top before coming to rest? Does its velocity decrease more slowly now?
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
Example: pushing a box across the floor so that it moves with a constant velocity.
Four forces act on the box — the applied push forwards, the force of friction backwards, the weight downwards and the normal force from the floor upwards.
The weight and the normal force are already balanced (Fig. $\displaystyle 6.11$).
If you now push with a force exactly equal in magnitude to the force of friction, those two also balance, so the net force becomes zero even though four forces are acting.
The box then keeps moving with constant velocity, as in Example 6.2.
Another everyday case: a weightlifter holding a barbell steady — the upward push she adds makes the net force on the barbell zero.
