12.4 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE
m70 cm- A rope is tied at twopoints which are 70 cmapart from each other, on the same horizontal line.
The total length of ropeis 1 m, and the maximum tension it can withstand is 1000 N. Find the
largest mass (m), in kg,that can be carried at the midpoint of the rope,without breaking the
rope. Include a labelleddiagram showing the triangle of forces in your answer.
More practice video solutions or help at http://www.everythingscience.co.za(1.) 01w9 (2.) 01wa (3.) 01wb (4.) 01wc (5.) 01wd (6.) 01we
(7.) 01wf (8.) 01wg (9.) 01wh12.4 Forces between Masses
ESBFC
In Grade 10, you saw that gravitational fields exert forces on masses inthe field. A field is a region
of space in which an object experiences a force. The strength of a fieldis defined by a field strength.
For example, the gravitational field strength, g, on or near the surfaceof the Earth has a valuethat is
approximately 9,8 m·s−^2.
The force exerted by a field of strength g on an object of mass m is given by:F = m· g (12.1)This can be re-written interms of g as:
g =F
m
This means that g can be understood to be a measure of force exerted per unit mass.
The force defined in Equation 12.1 is known as weight.
Objects in a gravitational field exert forces on each other without touching. The gravitational force is
an example of a non-contact force.
Gravity is a force and therefore must be described by a vector - so remember that gravity has both
magnitude and direction.Newton’s Law of Universal Gravitation ESBFD
DEFINITION: Newton’s Law of Universal Gravitation
Every point mass attractsevery other point mass by a force directed alongthe line con-
necting the two. This force is proportional to the product of the massesand inversely
proportional to the square of the distance between them.