Video Lecture 1: Pushes and Pulls — Net Vector Forces and Their Physical Manifestations

# Video Lecture 1: Pushes and Pulls — Net Vector Forces and Their Physical Manifestations
**Instructor:** Dr. Ananya Sharma | **Duration:** ~05:50 mins

### Introduction: What is a Force?
Whenever you open a door, kick a soccer ball, stretch a rubber band, or hit a tennis ball, you interact with matter. In physics, a **push or a pull** exerted upon an object resulting from its interaction with another object is called a **Force**.
- A force cannot exist in isolation; it requires an **interaction** between at least two objects.
- The standard SI unit of force is the **Newton (N)**.

### Vector Addition: Combining Forces
Forces have both magnitude and direction:
1. **Forces acting in the same direction:** They reinforce each other. The net force is their scalar sum: $F_{\text{net}} = F_1 + F_2$.
2. **Forces acting in opposite directions:** They oppose each other. The net force is the difference between the two forces: $F_{\text{net}} = |F_1 - F_2|$, acting in the direction of the larger force. (In a tug-of-war, if both teams pull with an equal force of 500 N, the net force is zero and the rope remains stationary!).

### Four Principal Effects of Force:
1. A force can move a stationary object (e.g., kicking a resting football).
2. A force can change the speed of a moving object (e.g., pedalling harder or applying bicycle brakes).
3. A force can alter the direction of motion (e.g., a batsman deflecting a fast cricket ball).
4. A force can change the shape or size of an object (e.g., rolling dough or compressing a foam sponge).