Force and Motion

• What happens to an object when a resultant force acts on it?

  It accelerates in the direction of the force
• What does it mean if an object is not accelerating?

  The resultant force on it is zero
• How can an object change its velocity?

  By changing its direction or speed
• What is the equation for resultant force?

  F = ma
• What does Newton's second law state about acceleration?

  It is proportional to resultant force
• How does mass affect acceleration for a given force?

  Greater mass results in smaller acceleration
• What is inertia?

  Tendency to stay at rest or uniform motion
• How can you investigate the link between force and acceleration using a trolley?

  • Vary the force applied to a constant mass
  • Use a motion sensor to record velocity
  • Pull the trolley with a known force
  • Repeat with different forces
• How can you investigate the effect of mass on acceleration?

  • Keep force constant
  • Increase mass by adding weights
  • Measure acceleration with a motion sensor
• What happens to acceleration if the resultant force on an object increases?

  Acceleration increases
• What is the resultant force on a car with mass 1200 kg and acceleration 2.0 m/s²?

  2400 N
• What is the weight of an object?

  Force acting on it due to gravity
• How does an object fall under the influence of gravity?

  It accelerates at about 10 m/s²
• What is terminal velocity?

  Velocity when weight equals frictional force
• What happens to the resultant force at terminal velocity?

  It is zero
• What is the difference between weight and mass?

  Weight is force; mass is matter quantity
• What is the equation for weight?

  W = mg
• What is gravitational field strength?

  Force on a 1 kg object in N/kg
• What happens to an object falling through a fluid?

  It experiences drag force resisting motion
• What is air resistance?

  Drag force for objects falling through air
• Why does an object initially accelerate when dropped in a fluid?

  Gravity is the only force acting on it
• What happens to the acceleration of an object falling through a fluid over time?

  It decreases until terminal velocity is reached
• What factors affect a vehicle's stopping distance?

  Thinking distance and braking distance
• What increases braking distance?

  High speed and poor weather conditions
• What factors increase thinking distance?

  Poor reaction time and high speed
• What does F=ma represent in braking force?

  Braking force of a vehicle
• What is the equation for deceleration?

  v = u² + 2as
• What does the law of conservation of momentum state?

  Total momentum before equals after interaction
• What is the equation for momentum?

  p = mv
• What is the unit of momentum?

  kg m/s
• What is an elastic object?

  Returns to original shape after deformation
• What is extension in relation to an elastic object?

  Difference between length and original length
• What is Hooke's law?

  Extension is directly proportional to force applied
• What happens beyond the limit of proportionality?

  Extension is no longer proportional to force
• What is the formula for the resultant force acting on an object?

  F=ma
• Why is a resultant force needed to make an object change direction?

  Acceleration is a change in velocity, and an object can change its velocity by changing its direction, even if it is travelling at a constant speed
• What does Newton's second law of motion state?

  The acceleration of an object is proportional to the resultant force on the object and inversely proportional to the mass of the object
• If the resultant force on an object increases, what happens to its acceleration?

  The acceleration increases
• What is the resultant force on a car of mass 1200 kg if its acceleration is 2.0 m/s²?

  $2400 \text{ N}$
• What is the weight of an object?

  The force acting on the object due to gravity