1c-Forces, movement, shape and momentum Flashcards
What is Newton’s First Law of Motion?A:
An object will remain at rest or in uniform motion unless acted upon by an external force.
What is Newton’s Second Law of Motion?
A: The acceleration of an object is directly proportional to the force applied and inversely proportional to its mass.
F=Ma
where:
F= force (N)
M= mass (kg)
a= acceleration (m/s²)
What is Newton’s Third Law of Motion?
A: For every action, there is an equal and opposite reaction.
What is the difference between weight and mass?
Mass (kg): The amount of matter in an object (scalar quantity).
Weight (N): The force due to gravity acting on an object’s mass.
W=mg
where:
W= weight (N)
m= mass (kg)
g= gravitational field strength (9.8 N/kg on Earth)
Q: What forces act on a falling object?
1.Gravity pulls the object downward.
2.Air resistance opposes motion.
3.Terminal velocity occurs when air resistance equals weight, resulting in constant velocity.
Q: What factors affect terminal velocity?A:
Mass (heavier objects have a higher terminal velocity)
Shape and surface area (larger surface area increases air resistance)
Density of the fluid (higher density increases drag)
Momentum and Conservation of Momentum
Q: What is momentum?
Momentum is the product of an object’s mass and velocity.
P=mv
where:
p = momentum (kg·m/s)
m= mass (kg)
v= velocity (m/s)
What is the principle of conservation of momentum?
A: In a closed system, total momentum before a collision equals total momentum after a collision.
Q: What is an impulse?
Q: Impulse is the change in momentum of an object when a force is applied over a period of time.
F x (change in time) = change in p
where change in p is the change in momentum.
What is work done?
A: Work is done when a force moves an object in the direction of the force.
W=fd
W= work done (J)
f= force (N)
d= distance moved in direction of force (m)
What is kinetic energy?
A: The energy an object has due to motion.
What is gravitational potential energy (GPE)?
The energy stored in an object due to its height above the ground.
what is power
A: Power is the rate of energy transfer.
Practical: Investigating Forces and Motion
Investigating Newton’s Second Law
1️⃣ Place a trolley on a frictionless track with a pulley system.
2️⃣ Attach a hanging mass to the trolley via a string over a pulley.
3️⃣ Release the trolley and use light gates (or a stopwatch) to measure acceleration.
4️⃣ Repeat with different masses on the trolley and varying forces (by changing the hanging mass).
5️⃣ Plot a graph of acceleration vs force and acceleration vs mass to observe relationships.
Key Findings:
✅ Acceleration increases as force increases (directly proportional).
✅ Acceleration decreases as mass increases (inversely proportional).
Practical: Investigating Forces and Motion
Measuring Terminal Velocity in Fluids
Method: Drop a ball bearing in oil and measure velocity over time.
Observation: The ball reaches terminal velocity when forces balance.
Initially, object accelerates due to gravity.
Drag force (fluid resistance) increases with speed.
When drag force = weight, the object stops accelerating and moves at constant velocity (terminal velocity).
1️⃣ At the start: When the ball is first dropped, only gravity acts on it, pulling it downwards. There is little to no drag force yet, so it accelerates quickly.
2️⃣ As it falls: The ball speeds up, and as its velocity increases, the drag force (fluid resistance) also increases. Drag force opposes motion, making it harder for the ball to keep accelerating.
3️⃣ Reaching terminal velocity: Eventually, the drag force becomes equal to the weight (gravitational force). At this point, the forces are balanced, and the ball moves at a constant velocity – this is called terminal velocity.
