With examples, explain any two of Newton’s laws of motion.
1. A body continues in its state of rest or uniform motion in a straight line unless acted upon by an external force.
For example, a book remains stationed on a table until an external force is applied or a moving ball on flat smooth surface will keep rolling indefinitely at the same speed and in the same direction unless friction from the ground or an obstacle (like a player’s foot) acts on it to change its state of motion.
2. The rate of change of momentum of a body is directly proportional to applied force and takes place in the direction of the force.
Examples:
Pushing a Cart: If you push an empty shopping cart, it accelerates more quickly compared to when it is full of groceries. This is because the mass of the empty cart is less, so a given force results in greater acceleration. Conversely, the same force applied to the heavier cart results in less acceleration.
Car Acceleration: When you press the gas pedal in a car, the engine generates a force that accelerates the car. The heavier the car (more mass), the more force is needed to achieve the same acceleration.
3. For every action, there is an equal and opposite reaction
(a). Rocket Propulsion:
- Action: The rocket expels exhaust gases out of its engines at high speed.
- Reaction: The rocket itself is pushed in the opposite direction, propelling it forward. This is how spacecraft and rockets are launched into space.
(b). Walking:
- Action: When you walk, your foot pushes backward against the ground.
- Reaction: The ground pushes your foot forward with an equal and opposite force, propelling you ahead.
(c). Swimming:
- Action: When a swimmer pushes the water backward with their hands and feet.
- Reaction: The water pushes the swimmer forward, allowing them to move through the water.
(d). Bird Flight:
- Action: Birds push down and backward with their wings.
- Reaction: The air pushes the bird up and forward, enabling flight.
(e). Recoil of a Gun:
- Action: When a bullet is fired, the gun exerts a force on the bullet to propel it forward.
- Reaction: The bullet exerts an equal and opposite force on the gun, causing it to recoil backward.
Thank you
Dr. Bbosa Science
