5.16 Newton's second law
9 exam questions worth 23 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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A resultant force of 60 N acts on a mass of 12 kg. Calculate the acceleration.
Mark scheme
a = F ÷ m (1); 60 ÷ 12 (1); 5.0 m/s² (1)
Model answer
a = F / m = 60 / 12 = 5.0 m/s².
A cyclist and bike have a total mass of 80 kg. They accelerate at 1.5 m/s². Calculate the resultant force.
Mark scheme
F = m a (1); 80 × 1.5 (1); 120 N (1)
Model answer
F = m a = 80 × 1.5 = 120 N.
A force of 15 N gives an object an acceleration of 3.0 m/s². Calculate the mass of the object.
Mark scheme
m = F ÷ a (1); 15 ÷ 3.0 (1); 5.0 kg (1)
Model answer
m = F / a = 15 / 3.0 = 5.0 kg.
A car of mass 1200 kg has a driving force of 4000 N and resistive forces of 1600 N. Calculate its acceleration.
Mark scheme
resultant force = 4000 − 1600 = 2400 N (1); a = F ÷ m (1); 2400 ÷ 1200 (1); 2.0 m/s² (1)
Model answer
Resultant force = 4000 − 1600 = 2400 N. a = F / m = 2400 / 1200 = 2.0 m/s².
A force acts on a trolley. The mass of the trolley is doubled. Describe what happens to the acceleration, if the force stays the same.
Mark scheme
the acceleration is halved (1); because acceleration is inversely proportional to mass (1)
Model answer
The acceleration halves, because it is inversely proportional to the mass.
A constant resultant force acts on an object. Describe how the force changes the acceleration if the force is doubled.
Mark scheme
the acceleration doubles
Model answer
The acceleration doubles.
Explain why a heavy and a light object, dropped from the same height in a vacuum, hit the ground at the same time.
Mark scheme
the only force is weight, W = m g (1); a = W ÷ m = g (1); so the acceleration is the same for both, as mass cancels (1)
Model answer
The only force is weight, so a = W / m = m g / m = g. The mass cancels, so the acceleration is 9.8 m/s² for both.
A lorry is full of cargo and a car is empty. Both have the same driving force. Explain why the car accelerates faster.
Mark scheme
the car has a smaller mass (1); so a larger acceleration for the same force (a = F ÷ m) (1)
Model answer
The car has a smaller mass, so the same force gives it a larger acceleration (a = F / m).
(Higher) Explain what is meant by inertial mass.
Mark scheme
a measure of how difficult it is to change the velocity of an object (1); the ratio of force over acceleration (1)
Model answer
Inertial mass measures how hard it is to change an object's velocity. It is the ratio of force to acceleration, m = F / a.
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