Suspended Block 1J30.10
Mechanics Statics of Rigid Bodies Resolution of Forces

Concept

Explain that the 50N weight of the car can be resolved into components of 30N parallel to the incline and 40N perpendicular to the incline and that these values are determined by the geometry of the 3-4-5 incline. Thus, the 50N weight of the car can be balanced (canceled) by the 30N and 40N tensions provided by the two cables.

Procedure

  1. Weigh the cart to show that it is 5kg.
  2. Set the car on the incline to show that it rolls down the incline in the absence of other forces.
  3. Ask your students: “Given an incline plane with sides 3, 4, and 5 units long, what should the masses of the parallel and perpendicular components to the incline be in order to balance the 5 kg car?”
  4. Thread the cable through the pulley at the top of the incline and hang three 1kg weights from its end.
  5. Thread the other cable through the other pulley and hang four 1kg weights from its end.
  6. Move the cart so that the cables are perpendicular to each other.
  7. Move the incline away from the cart and show that the cart is in static equilibrium. Thus, the weight of the 5kg car is supported by the parallel tension provided by a 3kg mass and perpendicular tension provided by a 4kg mass.

Equipment

  1. Suspended Block Apparatus
  2. Suspended Block Cart (5 kg)
  3. (7) 1 kg Weights
  4. 100 Newton Scale