Newton's Laws of Motion

• What does Newton's First Law of Motion state?

  Objects will remain at rest, or move with a constant velocity unless acted on by a resultant force
• What happens if the resultant force acting on an object is zero?

  The object will remain stationary if it was stationary before or continue to move at the same velocity if it was moving
• How does an object behave if it was moving before and the resultant force is zero?

  It will move at the same speed and in the same direction as before
• What is required for an object to move with a constant velocity?

  • The forces acting on the object must be balanced
  • The resultant force must be zero
• Is the Moon's orbit around the Earth an example of Newton's First Law of Motion? Explain.

  No, because the Moon is not moving with a constant velocity as it continually changes direction
• What does Newton's Second Law of Motion state?

  The acceleration of an object is proportional to the resultant force acting on it and inversely proportional to the object's mass
• What happens to an object's acceleration if the resultant force increases?

  The larger the resultant force, the larger the acceleration
• How does mass affect acceleration for a given force?

  The greater the object's mass, the smaller the acceleration experienced
• What is the equation for Newton's second law?

  F = ma

  
• What do the symbols in the equation F = ma represent?

  F = resultant force in Newtons (N), m = mass in kilograms (kg), a = acceleration in metres per second squared (m/s²)

  
• How do you calculate acceleration using the change in velocity?

  a = \frac{\Delta v}{t}

  
• If a car has a mass of 900 kg and accelerates at 9 m/s², what is the force required?

  F = 900 \times 9 = 8100 \text{ N}
• What happens to acceleration when the mass of an object increases while the force remains constant?

  Acceleration decreases because it is inversely proportional to mass

  
• How do you estimate quantities in realistic scenarios using Newton's second law?

  Use the symbol ~ to indicate an approximate answer
• If a passenger in a car has a mass of about 70 kg and the car decelerates at approximately -200 m/s², what is the force on the passenger?

  F \approx 70 \times -200 \approx -14000 \text{ N}
• What are the variables in the experiment investigating the effect of varying force on acceleration?

  • Independent variable: force, F
  • Dependent variable: acceleration, a
  • Control variables: mass, m
• What are the variables in the experiment investigating the effect of varying mass on acceleration?

  • Independent variable: mass, m
  • Dependent variable: acceleration, a
  • Control variables: force, F
• What is the aim of the experiment investigating the effect of varying force on acceleration?

  • To investigate the effect of varying force on the acceleration of an object of constant mass
• What is the aim of the experiment investigating the effect of varying mass on acceleration?

  • To investigate the effect of varying mass on the acceleration of an object produced by a constant force
• What equipment is used in the experiments investigating force and acceleration?

  • Metre ruler (resolution = 1 mm)
  • Stopwatch (resolution = 0.01 s)

  
• What is the method for measuring the effect of force on acceleration?

  1. Measure intervals on the bench
  2. Attach a pulley and string to a toy car
  3. Release the car and time its movement
  4. Record results and repeat with varying weights

  
• What is the method for measuring the effect of mass on acceleration?

  1. Measure intervals on the bench
  2. Attach a pulley and string to a toy car with a mass
  3. Release the car and time its movement
  4. Record results and repeat with varying masses

  
• How do you analyze results from the experiments on force and acceleration?

  • Determine average speed between intervals
  • Calculate acceleration using distance and time
  • Compare acceleration for different weights or masses

  
• What is the aim of Experiment 2?

  The aim is to investigate the effect of varying mass on the acceleration of an object produced by a constant force.
• What is the independent variable in the experiment?

  The independent variable is mass, m.
• What is the dependent variable in the experiment?

  The dependent variable is acceleration, a.

  
• What are the control variables in the experiment?

  The control variable is force, F.
• What is the method for conducting the experiment?

  1. Measure intervals on the bench using a metre ruler.
  2. Attach the bench pulley to the end of the bench.
  3. Put a 200 g mass on the car.
  4. Tie string to the toy car and pass it over the pulley.
  5. Select a weight for the weight hanger to gently accelerate the car.
  6. Hold the car at the start point and release it simultaneously with starting the stopwatch.
  7. Record results and repeat for increasing mass on the car (400 g, 600 g, 800 g, 1000 g).

  
• How do you calculate the average speed of the trolley?

  Use the distance between each interval and the average time to calculate average speed.
• What equation is used to calculate acceleration in the experiment?

  Acceleration is calculated using the formula: $a =$$\frac{F}{m}$.

  
• What should you do to minimize random errors in timing measurements?

  Take repeat readings and calculate an average to minimize timing errors.
• What is a systematic error mentioned in the experiment?

  Weights removed from the weight hanger must be transferred to the toy car or trolley.
• What safety consideration is mentioned for the experiment?

  Don't stand directly beneath the weight hanger to avoid falling weights.
• What does Newton's third law of motion state?

  It states that whenever two bodies interact, the forces they exert on each other are equal and opposite.

  
• How do force pairs work according to Newton's third law?

  If object A exerts a force on object B, then object B exerts an equal and opposite force on object A.

  
• How does Newton's third law explain walking?

  The foot pushes the ground backwards, and the ground pushes the foot forwards.

  
• What is inertia defined as?

  Inertia is the tendency of an object to continue in its state of rest or uniform motion unless acted upon by an external force.
• What is the relationship between inertial mass and acceleration?

  Larger inertial masses will experience smaller accelerations.
• How is inertial mass defined mathematically?

  Inertial mass is defined as $m =$$\frac{F}{a}$.
• Which object has the largest inertial mass if Object A accelerates at 1.5 m/s², Object B at 0.7 m/s², and Object C at 2.0 m/s²?

  Object B has the largest inertial mass because it has the smallest acceleration.