Question

Three masses 5 kg, 2 kg and 7 kg are aligned in a straight line as shown below. Find the net gravitational force on 4 kg?

• A. Zero
• B. 33.5 × 10^-11 N
• C. 46.69 × 10^-11 N
• D. 13.19 × 10^-11 N

Answer 1

The correct option is D

13.19 × 10^-11 N

5 kg and 7 kg masses attract the 4 kg mass in opposite direction.So, the net force is subtraction.

The gravitation force due to 5 kg on 4 kg is:

F = $\frac{GmM}{d^2}$

F = 5 $\times$ G = $33.5\times {10}^{-11}$ N ( The direction of force is towards 5 kg mass)

The gravitational force due to 7 kg on 4 kg:

F = $\frac{GmM}{d^2}$

F = 7 $\times$ G = $46.69\times {10}^{-11}$ N (the direction of force is towards 7 Kg mass)

Since the force on 2 kg masses due to 5 kg mass is opposite to the force due to 7 kg on 2 kg mass. The net force is the subtraction of both the forces.

Net force on 2 kg mass = (46.69 - 33.5) $\times$ 10^-11N = 13.19 $\times$ 10^-11 N.