Question

An object of mass $2kg$ is sliding with a constant velocity of $4m{s}^{-1}$ on a frictionless horizontal table. The force required to keep the object moving with the same velocity is

• A. $32N$
• B. $0N$
• C. $2N$
• D. $8N$

Answer 1

The correct option is B

$0N$

Step 1: Given and to find

An object of mass $2Kg$ is sliding with a constant velocity of $4m{s}^{-1}$ on a frictionless horizontal table.

Step 2: Formula

1. Newton’s second law of motion, $F=ma,F$ is the applied force that is to be determined. $m$ is the mass and $a$ is the acceleration of the mass.
2. As motion is kept uniform, the substitution of $a=0$ the required force can be determined.

Step 3: Finding The force required to keep the object moving with the same velocity

1. According to Newton’s Second Law of Motion rate of change of momentum of an object is directly proportional to the force applied, or, for an object with constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration.
2. The velocity of the mass is. $4m{s}^{-1}$ The table is frictionless.
3. Therefore, to keep its velocity the same its acceleration will be. $a=0$ Hence, the required force will be:

$$\begin{gathered} F=ma \\ \mathrm{and}\mathrm{as}a=0 \\ \Rightarrow F=m\times 0 \\ \Rightarrow F=0N \end{gathered}$$

Hence, the force required to keep the object moving with the same velocity is $0N$. Hence option (b) is correct.