Question

q.7. which of the following pictures is an example of newtons first law of motion? q.8. two 15 n forces in opposite directions are acting on an object. what is the magnitude of the net force? 0 n 10 n 20 n 30 n q.9. two 15 n forces in the same direction are acting on an object. what is the magnitude

Explanation:

Step1: Recall Newton's first - law concept

Newton's first law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Step2: Analyze each picture

The picture of a person in a car with a seat - belt and an air - bag deploying during a sudden stop is an example. The person's body wants to continue moving forward due to inertia (Newton's first law) when the car suddenly stops.

Step3: Solve net - force problem for Q.8

Net force when two equal and opposite forces act on an object: Let the two forces be $F_1 = 15N$ and $F_2=- 15N$ (opposite direction). Net force $F_{net}=F_1 + F_2=15+( - 15)=0N$.

Step4: Solve net - force problem for Q.9

Net force when two forces act in the same direction: Let the two forces be $F_1 = 15N$ and $F_2 = 15N$. Net force $F_{net}=F_1+F_2=15 + 15=30N$.

Answer:

Q.7: The picture of a person in a car with a seat - belt and air - bag deploying during a sudden stop
Q.8: 0N
Q.9: 30N