Forces and Motion
4 marks · EasyA small mass is released from rest and falls freely under gravity. The mass is 0.30 kg. (Assume air resistance is negligible and g = 10 N/kg.)
State the unit of weight in the SI system.
Calculate the weight of the mass.
Explain why the velocity of the mass increases as it falls.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) newton
(b) 3 N
(c) The force of gravity acts downwards and causes an unbalanced force, so the mass accelerates and its velocity increases.
Common mistakes: Weight given in kg instead of N; Calculating weight as mass
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States the correct SI unit for weight as newton (N)
M1 (b) · 1 mark · Writes weight = mass × gravitational field strength (W = m × g) or shows substitution
A1 (b) · 1 mark · Correctly calculates weight as 3 N, allows rounding to 3.0 N
B2 (c) · 1 mark · Provides a suitable explanation linking unbalanced force of gravity with increasing velocity (acceleration due to gravity)
Worked solution
a) The SI unit for weight is the newton (N).
Substituting the values:
c) The velocity increases because gravity is the only force acting, so there is an unbalanced force that makes the mass accelerate as it falls.