Homework 7.2 solutions
1
(a)
A point mass of weight 6.2N is acted on by a horizontal force of 3.8N.
Calculate the resultant of these two forces.
magnitude: _____ N
(b)
Determine the magnitude and direction of a third force acting on the object for it to be in
equilibrium.
magnitude: _____ N
2
direction: _____  anticlockwise to horizontal
direction: _____  anticlockwise to horizontal
A small object of weight 5.4N is at rest on a rough slope, which is at an angle of 30 to the
horizontal.
(a)
Sketch a diagram and show all three forces acting on the object.
(b) i
Calculate the frictional force on the object.
(b)ii
Calculate the support force from the slope on the object.
3
An archer pulled a bowstring back until the two halves of the string are at 140 to each other (see
diagram below). The force is needed to hold the string in this position was 95N.
70
force to hold
arrow in place
70
arrow
(a)
Calculate the tension in each part of the bowstring in this position.
(b)
Calculate the resultant force on an arrow at the instant the bowstring is released.
4
An elastic string is stretched horizontally between two fixed points 0.80m apart. An object of
weight 4.0N is suspended from the midpoint of the string, causing the midpoint to drop a distance
of 0.12m.
(a)
Calculate the angle of each part of the string to the vertical.
(b)
Calculate the tension in each part of the string.
Hints and solutions: http://mathsurgery.wikispaces.com/Phys+AS+unit+2+section+7.2+-+equilibrium+and+balanced+forces