12.6 CHAPTER 12. FORCE,MOMENTUM AND IMPULSE
P rope S
70 ◦
strut
rope R
box
(a) Draw a diagram (with labels) of all the forces acting at the point P, when P is in
equilibrium.
(b) By resolving the force exerted by rope R intocomponents, calculate the...
i. magnitude of the force exerted by rope S.
ii. mass, m, of the box.
(c) Will the tension inrope R, increase, decrease or remain the sameif rope S is
pulled further to the right (the length of rope R remains the same)? Give areason
for your choice.
- A tow truck attempts to tow a broken down car of mass 400 kg. The coefficient of
static friction is 0,60 and the coefficient of kinetic (dynamic) friction is0,4. A rope
connects the tow truck to the car. Calculate theforce required:
(a) to just move the carif the rope is parallel tothe road.
(b) to keep the car moving at constant speed ifthe rope is parallel to the road.
(c) to just move the carif the rope makes an angle of 30◦to the road.
(d) to keep the car moving at constant speed ifthe rope makes an angle of 30◦to
the road.
- A crate weighing 2000 N is to be loweredat constant speed downskids 4 m long,
from a truck 2 m high.
(a) If the coefficient of sliding friction between the crate and the skids is0,30, will
the crate need to be pulled down or held back?
(b) How great is the force needed parallel to theskids?
- Block A in the figures below weighs 4 N and block B weighs 8 N. The coefficient of
kinetic friction betweenall surfaces is 0,25. Findthe force P necessary todrag block
B to the left at constantspeed if
(a) A rests on B and moves with it
(b) A is held at rest
(c) A and B are connected by a light flexible cord passing around a fixedfrictionless
pulley
A
B
A
B
A
B
P P P
(a) (b) (c)
Gravitation
- [SC 2003/11]An object attracts another witha gravitational force F. If the distance
between the centres of the two objects is now decreased to a third (^13 ) of the original
distance, the force of attraction that the one object would exert on theother would
become...
