# SPH3U Dynamics Test Review Outline

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```					                                                                                                SPH3U - Forces

SPH3U Dynamics Test Review Outline
Format:
15 marks multiple choice, 25 marks short answer (calculate/explain)
All Forces Unit Equations will be provided, Big 5 Equation sheets may be used

Topics and Concepts:                                Textbook pages and recommended study materials:
   Newton’s First, Second and Third Laws                Readings: pp. 119-130, 136-138, 152-160, 162-172,
175-177
   inertia and mass
    Forces worksheet (problems combining forces and
   balanced and unbalanced forces
kinematics)
   force pairs (action and reaction force
    FBD worksheet
pairs)
    Newton’s First and Second Law quiz
   forces are vectors and can be added up
like vectors                                         class notes, example problems
       
   net force, Fnet  ma                                 http://www.physicsclassroom.com/Class/index.cfm

   free body diagrams (FBDs)
   normal force
       
   friction – static and kinetic ( F f  FN )

   mass, weight, force due to gravity
( Fg  mg , g = 9.8 N/kg)

Gm1m2
   universal gravitation ( Fg          ,G=
r2
6.67 × 10-11 Nm2/kg2)
   Fundamental Forces

Forces:
p. 143 – 3, 4, 5, 6, 8, 10, 14, 16, 19, 20, 22, 23, 25, 26, 27, 29, 31, 35, 36, 37, 38, 39, 42, 44, 53, 54
p. 181 – 20, 21, 28, 32, 36, 37, 38, 39, 44, 46, 47, 48

Some Force Problems:
1. Explain what headrests, airbags and seatbelts in cars and whiplash have to do with Newton’s laws of
motion.

2. Julien steps onto a dock off a boat that is tied securely and close to the dock. Meanwhile, Dylan steps
off her boat when it is not yet attached to the dock. Use Newton’s laws to explain what happens in
each case.

3. A block of mass 15.0 kg, starting from rest, is pulled along a rough horizontal tabletop by a constant
force. The coefficient of friction (kinetic) is 0.3. It is found that this body moves a distance of 5.0 m
in 4.0 s.
a) What is the force of friction acting on the body? (44 N)
b) What is the acceleration of the body? (0.63 m/s2)
SPH3U - Forces

c) What constant force is being applied to the body? (54 N)
4. Henry drives Car A, of mass 1000 kg, at 100 km/h, and brakes to a stop. Jaiden drives Car B, of equal
mass, at 50 km/h and also brakes to a stop. Assume that the braking force is constant and the same for
both vehicles, and compare the braking distances for the cars. (Car A’s braking distance is 4x that of
Car B’s)

5. Carly drives Car C, of mass 2000 kg, at 50 km/h and brakes to a stop with the same braking force as
in the previous question. Compare the braking distance of Car C to car A. (Car C’s braking distance is
2x that of Car A’s)

6. Draw FBDs for each of the following cases. Neglect air resistance.
The rock is tied to a rope                                  The rock is slowing
and is pulled upward                                        down due to friction.
such that it is accelerating
up.

7. Mariela and Alex pin a giant salamander (50 kg) against a wall with a force of 1500 N so that it is
suspended off the ground without slipping. What is the coefficient of static friction that allows them
to do this? (0.33)

8. Tatiana, floating in space at some distance above the earth’s surface, notices that the force of gravity
she is experiencing from the earth is one-quarter what she would feel at the surface of the earth. How
far away is she from the centre of the earth, in terms of the earth’s radius? How far above the surface
of the earth is she, in terms of the earth’s radius? The radius of the earth is 6.38 × 106 m, and the mass
of the earth is 5.98 × 1024 kg. (twice the radius, one radius)

9. Xhorxhia, on a sunny resort beach, measures the gravitational attraction between her and a mysterious
stranger 50 m away to be 1.067 × 10-10 N. Assuming she has a mass of 50 kg, what is the mass of the
mysterious stranger? (80 kg)

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Jun Wang Dr
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