FORCES AND SHAPE
3 marks · NormalA toy boat floats on a lake and is pulled forwards by a string with a force of 5 N. At the same time, water resistance acts on the boat with a force of 3 N in the opposite direction.
Draw a labelled diagram showing all the forces acting on the boat. Indicate the directions clearly.
Calculate the resultant force acting on the boat. State its direction.
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) — · must show Arrow labelled 5 N forward (string pull), arrow labelled 3 N backward (water resistance)
(b) 2 N forwards N · must show Subtraction shown, Final answer with direction
Must show: correct arrows for both forces, correct direction, labels
Common mistakes: Forgetting direction; Drawing forces on the wrong side
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Draws and labels arrows: 5 N forward and 3 N backward.
M1 (b) · 1 mark · Subtracts water resistance from string force: 5 N - 3 N.
A1 (b) · 1 mark · Correct final answer: 2 N forwards.
Worked solution
Resultant force = 5 N (forwards) - 3 N (backwards) = 2 N forwards.