In the diagram on the right, a plank weighing 120 N is supported by two trestles at points A and B. A man weighing 480 N is standing on 1m mass centre of of plane the plank.. a Redraw the diagram, showing all the forces acting on the plank. b Calculate the total clockwise moment of the two weights about A. c Use the principle of moments to calculate the upward force from weight of man 480 N weight of plank 120 N the trestle at B. d What is the total downward force on the tresties? tist e What is the upward force from the trestle at A? f The man now walks past A towards the left-hand end of the plank. What is the upward force from the trestle at 8 at the instant the plank starts to tip? g How far is the man from A as the plank tips

An object moves from position +34m to the position -15m in 15 seconds. what is the total displacement? what is the total velocity?

Selma made a diagram to compare convection and radiation. which label belongs in the area marked x? must involve temperature differences between substances or objects only occurs when molecules are in direct contact involves the movement of fluids based on density differences can occur where there is little or no matter

1. what is the relationship between wavelength and the penetrating power of an electromagnetic wave? a) the penetrating power has no relationship to the wavelength. b) the penetrating power increases as the wavelength increases. c) the penetrating power decreases as the wavelength increases. d) the penetrating power decreases as the wavelength decreases. 2. as ice melts and turns into water, the speed of sound through the material would most likely do what? justify your answer. a) the speed would not change because the material is always water. b) the speed of sound would increase because the density of water is less than that of ice. c) the speed of sound would increase because energy is added to ice in order to make it melt. d) the speed of sound would decrease because sound travels faster through solids than liquids. 3.which of these waves need a medium to travel through? a) sound b) x-rays c) infrared rays d) visible light