Topic 5 - Forces

• What is a force?

  A push or pull
• What are contact forces?

  Forces when objects are physically touching
• What are non-contact forces?

  Forces like magnetism and gravity
• How do contact forces relate to electrostatic repulsion?

  Contact forces arise from electrostatic repulsion
• What is a normal contact force?

  Force when pushing a door
• What are examples of contact forces?

  Friction, air resistance, and tension
• How can forces be represented?

  With vectors showing direction and magnitude
• What does the length of a force vector indicate?

  The magnitude of the force
• What is a resultant force?

  The sum of all forces acting on an object
• How do you find the resultant force when forces act in opposite directions?

  Add vectors, making one negative
• What is the resultant force if two forces of 5 N and 2 N act to the right?

  3 N to the right
• How do you find the resultant force of vectors at right angles?

  Use Pythagoras' theorem
• What does SOHCAHTOA refer to?

  Trigonometric relationships in right triangles
• What happens if forces are balanced?

  The object does not accelerate
• What is Newton's first law of motion?

  An object remains at constant velocity if no resultant force acts
• What is a scalar quantity?

  A quantity with magnitude only
• What is the difference between displacement and distance?

  Displacement includes direction, distance does not
• What is weight?

  Force due to gravity on an object
• How is weight calculated?

  Weight = mass × gravitational field strength
• What is the gravitational field strength on Earth?

  9.8 N/kg
• What is the weight of a 1 kg mass on Earth?

  10 N
• What must be true for forces to be balanced when lifting an object?

  Upward force equals the weight of the object
• What is the work done when lifting an object?

  Work done = force × distance moved
• What is the equation for gravitational potential energy gained?

  GPE = mass × G × height
• What does Hooke's law state?

  F = k × e (Force = spring constant × extension)
• What is the unit for spring constant?

  Newtons per meter
• What does it mean for a material to stretch elastically?

  It returns to its original shape after force removal
• What does a straight line through the origin in a force-extension graph indicate?

  Directly proportional relationship between force and extension
• What is a systematic error in measurement?

  An error that consistently skews results in one direction
• What is a random error in measurement?

  An error that varies unpredictably with each measurement
• What is the energy stored in a spring when extended?

  Energy = 0.5 × k × e²
• What is torque or moment?

  Turning force equal to force × distance to pivot
• What is the unit for torque?

  Newton meters
• What does the principle of moments state?

  Moments clockwise equal moments anticlockwise
• What is pressure?

  Pressure = force / area
• What is the unit for pressure?

  Newtons per square meter (Pascals)
• Why does pressure increase with depth in water?

  Due to weight of water above pushing down
• What is the equation for calculating pressure in a fluid?

  P = H × ρ × g
• What is the density of water?

  1,000 kg/m³
• What causes gas pressure?

  Collisions of gas particles with surfaces