Moments/Forces Flashcards
State 2 conditions that must be satisfied for the rod to be in equilibrium.
Net moment about a point is 0
Net force is 0
Explain what is meant by the centre of gravity.
The point where entire weight is thought to be concentrated.
State and explain, without calculation, how the minimum force that needs to be applied vertically at A to lift the rear wheels off the ground compares to the force you calculated in part (c).
It would be less
Larger distance to pivot
Smaller force can provide large enough moment.
State and explain where the glass should be positioned on the tray if the force, P, is to have the same value as in part (a).
Positioned in pivot
There’s no additional moments on it.
Equation for gravitational potential energy
E = mgh
Air enters the engine at A and is heated before leaving B at a much higher speed.
Explain, using appropriate laws of motion, why the air exerts a force on the engine in the forward direction.
rate of change of momentum so force acting on the air (Newton 2)
air exerts force of the same magnitude
but opposite in direction (Newton 3)
Explain how and why the maximum range of the wheelchair on level ground is
affected by
* the mass of the user
* the speed at which the wheelchair travels
Reduces the range
increases the friction on the tyres
Increasing the speed
Air resistance increases with speed
The student suggests that the forces exerted on the ruler by A and B act as a couple. Discuss whether his suggestion is correct.
- Two equal forces acting in opposite directions
- Forces don’t act in opposite directions
