In this question use g=9.8g = 9.8g=9.8 m s−2^{-2}−2
A stone of mass 0.4 kg is released from rest at a point 2.5 metres vertically above the surface of a lake.
The stone falls freely under gravity until it enters the water.
While the stone is moving through the water it experiences a constant resistance of magnitude 12 N, in addition to its weight.
Find the speed of the stone as it enters the water.
Find the magnitude of the deceleration of the stone while it is moving through the water.
Find the depth below the surface at which the stone first comes to instantaneous rest.
139 exam-style questions on AQA A Level Maths 3.3 R: Forces and Newton's laws, covering 3.3.1 Concept of a force and Newton's first law, 3.3.2 Newton's second law, 3.3.3 Weight and motion under gravity, 3.3.4 Newton's third law and equilibrium, 3.3.5 Addition of forces and resultants (A-level only), and 3.3.6 Friction (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.