P10
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State Newton’s Second Law of motion in words.
The acceleration of an object is proportional to the resultant force acting on it and inversely proportional to the mass of the object.
What is the formula linking resultant force, mass, and acceleration? Include the standard units for each.
𝐹=m×𝑎 F= Resultant Force (Newtons, N) m= Mass (kilograms, kg) a = Acceleration (metres per second squared, m/s^2
Define inertia and explain what inertial mass is.
Inertia: The tendency of an object to stay at rest or continue in uniform motion (remain at the same velocity). Inertial Mass: A measure of how difficult it is to change the velocity of an object. It is defined as the ratio of force / acceleration.
How can you calculate acceleration from a velocity-time graph?
Acceleration is equal to the gradient (slope) of the line on a velocity-time graph.
Calculate the resultant force required to make a 1,500kg car move at 2m/s
F=m x a F = 1,500 x 2 F = 3000N
An object has a mass of 5kg. If a resultant force 40N acts on it, what is the acceleration.
a = F / m a = 40 / 5 a = 8m/s^2
What is the difference between mass and weight?
Mass: The quantity of matter in an object, measured in kilograms (kg). It stays the same regardless of location. Weight: The force acting on an object due to gravity, measured in Newtons (N). It changes depending on the gravitational field strength.
Give the equation for weight, including the standard units.
W = m x g W = Weight (N, newtons) m = Mass (kg, kilograms) g = Gravitational Field Strength (Newtons per Kilogram N/kg)
Define the centre of mass of an object.
The single point at which the weight of an object can be thought of as acting.
Explain what happens to the resultant force and acceleration when an object reaches terminal velocity.
The frictional force (drag) equals the weight. The resultant force is zero. The acceleration is zero, and the object moves at a constant speed.
Describe the two main forces acting on an object falling through a fluid (like air or water).
Weight: Acts downwards (constant). Drag (Friction): Acts upwards (increases as the object speeds up).
If the gravitational field strength (g) on the Moon is 1.6N/kg, how does a person’s mass and weight compare to when they are on Earth?
Their mass stays exactly the same. Their weight decreases because g is much lower than Earth’s (9.8N/kg)
What are the two components that make up the total stopping distance of a vehicle?
Thinking distance + Braking distance. Thinking distance: The distance traveled during the driver’s reaction time. Braking distance: The distance traveled while the braking force is applied.
Name three factors that can increase a driver’s thinking distance.
Tiredness Alcohol or drugs Distractions (e.g., using a mobile phone).
Name three factors that can increase a vehicle’s braking distance.
Poor road conditions Poor vehicle maintenance Higher speed
Describe the energy transfer that occurs when a driver applies the brakes.
Work is done by the friction between the brakes and the wheels. This transfers kinetic energy from the vehicle into the thermal energy store of the brakes, causing them to get hot.
What is the formula used to calculate the work done by the brakes to stop a car?
W = F x s W= Work done (Joules, J) — this is equal to the initial kinetic energy. F= Braking force (Newtons, N). s= Braking distance (metres, m).
Why are very large decelerations dangerous for a vehicle?
They can cause the brakes to overheat, making them less effective. They can cause the tires to lose grip, leading to skidding and loss of control.
If the speed of a car doubles, what happens to the braking distance?
The braking distance quadruples
Define momentum and state its standard unit.
Momentum is the product of an object’s mass and its velocity. The unit is kilogram metres per second (kg m/s)
What is the formula for momentum? State the units for each variable.
p = m x v p = momentum (kg m/s) m = mass (kg) v = velocity (m/s)
State the law of conservation of momentum.
In a closed system, the total momentum before an event (like a collision or explosion) is equal to the total momentum after the event.
what is a “closed system”?
A system where no external forces (such as friction or air resistance) act on the objects involved.