91Ó°ÊÓ

1. T=W=65N ,
2. V=7.6m/s and
3. $a=2.4\mathrm{m}/{\mathrm{s}}^2$.

Newton’s second law states that the net force acting on the object is equal to the product of mass and the acceleration of the object.

Find the scale reading by using Newton’s law. We can find the mass of the object just using weight equation.

1. W=mg
2. F =ma

Here, W is weight of the object,m is mass of the object,g is gravitational acceleration, F is force and is acceleration of the object.

Mass of the object can be calculated using the formula for the weight.

$$\begin{gathered} W=mg \\ m=\frac{W}{g} \\ =\frac{65\mathrm{N}}{9.8\mathrm{m}/{\mathrm{s}}^2} \\ =6.6\mathrm{kg} \end{gathered}$$

Therefore, the mass of the object is 6.6kg.

As the cab is moving with constant speed the acceleration is zero so the scale reading will be 65N.

We apply Newton’s second law to find tension or scale reading,

$$\begin{gathered} ma=T-mg \\ T=ma+mg \\ =m\left(a+g\right) \\ =6.6\mathrm{kg}\left(-2.4\mathrm{m}/{\mathrm{s}}^2+9.8\mathrm{m}/{\mathrm{s}}^2\right) \\ =49\mathrm{N} \end{gathered}$$

Therefore, the tension or scale reading is 49N.