A boy (25kg) and a girl (20kg) are playing on a see-saw which is 4m long. If the boy sits 1m from the centre on the left side and the girl 2m from the centre on the other, which direction will the see-saw will rotate around its centre?
Student should calculate the moments about the pivot point (from diagram recognise this is the centre of the see-saw) for each child. Using the equation, moment = mass x acceleration x distance from pivot, with acceleration due to gravity = 9.81m/s^2 The moment for the boy is 25 x 9.81 x 1 = 245.25N anti-clockwise and, the moment for the girl is 20 x 9.81 x 2 = 392.4N clockwise. Therefore, the see-saw will rotate clockwise.
JL
Related Physics A Level answers
All answers ▸One of the decays of potassium (A=40, Z=19) results in an excited argon atom with excess energy of 1.50 Mev. In order to be stable, it emits a gamma photon. What frequency and wavelength has this gamma photon?
A ball of mass 0.25 kg is travelling with a velocity of 1.2 m/s when it collides with an identical, stationary ball. After the collision, the two balls move together with the same velocity. How fast are they moving?
A ball is dropped from rest at a height of 2 metres. Assuming acceleration due to gravity (g) is 10m/s^2 calculate the velocity of the ball just before it hits the floor.
An engineering student found that the Youngs modulus of an alloy was 2.8 x 10^11 Pa. The 1.5m wire of the allow increased in length by 0.24% during an experiment. Calculate the stress on the wire.