A level physics: Dynamics part 1 3.3

• What happens when a resultant force acts on a body with mass?

  The body will speed up with acceleration.
• What is the formula that relates mass, force, and acceleration?

  F = ma
• What does the relationship between resultant force and acceleration imply?

  Objects will accelerate if there is a resultant force acting upon them.
• What does an unbalanced force on a body indicate?

  It means the body experiences a resultant force.
• What effect does a resultant force along the direction of motion have on a body?

  It will speed up (accelerate) or slow down (decelerate) the body.
• What happens if the resultant force is at an angle to the direction of motion?

  It will change the direction of the body.
• What is the unit of force commonly used?

  The Newton (N).
• What is the SI unit for force?

  kgms⁻²
• How is one Newton defined?

  It is the force that will give a mass of 1 kg an acceleration of 1 ms⁻².
• What does it mean that force is a vector?

  Every force has a magnitude and direction.
• How is the resultant force determined?

  It is the vector sum of all the forces acting on the body.
• How can resultant forces be positive or negative?

  It depends on their direction.
• What is the significance of the angle in resultant forces?

  It requires vector addition or scale drawing to find magnitude and direction.
• How is acceleration classified as a vector?

  It can be either positive or negative depending on the direction of the resultant force.
• What does a resultant force in the same direction as motion indicate?

  The acceleration is positive.
• What does a resultant force in the opposite direction to motion indicate?

  The acceleration is negative.
• What happens to an object with a resultant force opposite to its motion?

  It will slow down and eventually come to a stop.
• What is the effect of ignoring drag forces on acceleration?

  The acceleration is independent of the mass of an object.
• What experiment demonstrates that a feather and a hammer fall at the same rate on the Moon?

  Astronauts dropped both from the same height.
• What is weight in terms of gravitational effect?

  Weight is the effect of a gravitational field on a mass.
• How is weight measured?

  It is measured in Newtons (N) and is a vector quantity.
• What is the relationship between weight and mass?

  The weight of a body is equal to the product of its mass (m) and the acceleration of free fall (g).
• What is the formula for calculating weight?

  W = mg
• What is the acceleration due to gravity on Earth?

  9.81 ms⁻² (or Nkg⁻¹)
• What is free fall?

  An object in free fall is falling solely under the influence of gravity.
• How do all free-falling objects behave on Earth?

  They accelerate towards Earth at a rate of 9.81 ms⁻².
• What happens to bodies near Earth in the absence of air resistance?

  All bodies fall with the same acceleration regardless of their mass.
• How does mass differ from weight?

  An object's mass always remains the same, but its weight differs depending on the strength of the gravitational field.
• What is the gravitational field strength on the Moon?1.63 Nkg⁻¹.
• What is the weight of a 70 kg object on Earth?

  $W =$$70 \text{ kg} \times 9.81 \text{ N/kg} =$$687 \text{ N}$
• What is the weight of a 70 kg object on the Moon?

  $W =$$70 \text{ kg} \times 1.63 \text{ N/kg} =$$114 \text{ N}$
• What is tension in physics?

  The force experienced by a cable, rope, or string when pulled, hung, rotated, or supported.
• How is normal contact force defined?

  It is the force arising when an object rests against another object acting at a 90° angle to the plane of contact.
• What does upthrust refer to?

  The upward buoyancy force acting on an object when it is in a fluid.
• What is friction?

  The force that arises when two surfaces are in contact with each other.
• How does friction behave in relation to motion?

  Friction always opposes the motion.
• What are free-body diagrams used for?

  • Modelling the forces acting on an object
  • Each force is represented as a vector arrow
  • Arrows are scaled to the magnitude of the force
  • Arrows point in the direction the force acts
  • Forces are labelled with their names
  • Used to identify forces in different planes
  • Resolve net force in a particular direction
• How can the net force in a particular direction be calculated?

  By using the labelled angles and magnitudes, resolving each force into horizontal and vertical components.
• What happens when a constant force acts upon an object?

  It will experience a resultant acceleration, determined using F = ma.
• What is the difference between one-dimensional and two-dimensional planes in motion?

  One-dimensional involves just up and down or left and right, while two-dimensional involves both directions.