Q.Give the magnitude and direction of the net force acting on

Concept: Newton's First Law (Inertia)

When an object moves with constant velocity (including zero velocity), the net force on it must be zero. This is the core idea — if there is no acceleration, the vector sum of all forces is zero.

Reasoning steps:

1. Constant speed means zero acceleration.
2. From Newton’s second law, $F_{\text{net}} = ma$, if $a = 0$ then $F_{\text{net}} = 0$.
3. Direction is irrelevant when the net force is zero.

1. Raindrop falling at constant speed → terminal velocity → net force = 0.
2. Cork floating stationary → buoyant force balances weight → net force = 0.
3. Kite held stationary → all forces (tension, lift, weight, drag) cancel → net force = 0.
4. Car moving at constant velocity on rough road → engine force exactly opposes friction → net force = 0.
5. Electron far from all fields → no interactions → net force = 0.
   ✓Final answer

   The net force in every case is $\boxed{0\ \text{N}}$.

1. Drop of rain falling at constant speed

   The raindrop is moving downward at a steady speed — that means its velocity is constant. By Newton’s First Law, if velocity is constant, acceleration is zero, so the net force must be zero.

   Two forces act on it: gravity (downward) and air resistance (upward). Since the speed is constant, these two exactly balance.

   Net force = 0 N

2. Cork of mass 10 g floating on water

   The cork is stationary on the water surface — velocity is zero and stays zero. Again, no acceleration means net force is zero.

   The forces are its weight (downward) and the buoyant force from water (upward). For the cork to float without sinking or rising, these must be equal and opposite.

   Net force = 0 N

3. Kite skillfully held stationary in the sky

   “Stationary” means velocity is zero and remains zero — so net force is zero.

   The kite experiences its weight (down), tension from the string (at an angle), and the lift from wind (at another angle). The person holding the string adjusts it so that all three forces cancel out exactly.

   Net force = 0 N

4. Car moving with constant velocity of 30 km/h on a rough road

   Constant velocity (even on a rough road) means zero acceleration, hence zero net force.

   The engine provides a forward driving force, while friction and air resistance act backward. On a rough road, friction is larger, but the driver adjusts the throttle so that the forward force exactly equals the total opposing force.

   Net force = 0 N

5. High-speed electron in space far from all material objects, free of electric and magnetic fields

   “Far from all material objects” means no gravitational pull from planets or stars. “Free of electric and magnetic fields” means no electromagnetic forces. So no forces at all act on the electron.

   Even though it’s moving at high speed, its velocity is constant (no forces to change it), so net force is zero.

   Net force = 0 N

Concept: Newton's First Law — constant velocity (including rest) means zero net force

Step 1: Recognise the common thread

In every part, the object described moves with constant velocity (including velocity = 0). Newton's second law, $F_{\text{net}}=ma$, tells us that zero acceleration means zero net force — regardless of how many individual forces are acting, they must sum to zero.

Step 2: Check each case

1. Raindrop at constant (terminal) speed: gravity balances air resistance.
2. Cork floating, stationary: weight balances buoyant force.
3. Kite held stationary: tension, weight, and aerodynamic lift/drag all cancel.
4. Car at constant velocity on a rough road: engine's driving force exactly balances friction + drag.
5. Electron far from all fields/matter: no forces act on it at all. Step 3: Conclude for each Since acceleration is zero in every case, $F_{\text{net}} = m(0) = 0$. Final Answer: Net force = 0 N in every case (a)–(e) — only the specific forces that cancel differ from case to case.