Exam 2 Chapters 5-8 PHYS 2048C Review
Understand the concept of Inertia and Newton’s 3 Laws of Motion. Know the equation for friction.
Review an Atwood’s Machine
Understand the concept of conservation of mechanical energy.
Review Kinetic Energy, Gravitational Potential Energy (near the surface of Earth), Elastic Potential
Energy, and Thermal Energy
Review the definition of work and the Work-Energy Theorem
Work done by a Conservative Force = - (Change in Potential Energy)
Review the concept and definition of Power
1. A sled is on an icy (frictionless) slope that is 34 degrees above the horizontal. When a 42-N force,
parallel to the incline and directed up the incline, is applied to the sled, the acceleration of the sled
is 2.0m/s2, down the incline. The mass of the sled is:
2. A box with a weight of 36-N rests on a horizontal surface. A person pulls horizontally on it with a
force of 12-N and it does not move. To start it moving, a second person pulls vertically upward on
the box. If the coefficient of static friction is 0.46, what is the smallest vertical force for which the
box moves?
3. A car is traveling at 20m/s on a horizontal road. The brakes are applied and the car skids to a stop in
3.2 seconds. The coefficient of kinetic friction between the tires and the road is:
4. A 60-N force is applied to a crate on a horizontal rough floor, causing it to move horizontally. If the
coefficient of kinetic friction is 0.60, in what direction should the force be applied to obtain the
greatest acceleration?
5. An automobile moves on a level horizontal road in a circle of radius 40m. The coefficient of friction
between the tires and road is 0.45. The maximum speed with which the car can round the curve is:
6. One end of a 2.0m long string is fixed, the other end is attached to a 3kg stone. The stone swings in
a vertical circle, with a uniform speed of 4.0m/s. Find the tension force of the string at the top point
and the bottom point.
7. 4000N is pulled across a frozen lake by a horizontal rope. The coefficient of kinetic friction is 0.08.
How much work is done in pulling the load 1100m if its speed is increasing at a constant rate of
0.22m/s2?
8. A man pushes a 70N crate a distance of 6.0m upward along a frictionless slope that makes an angle
of 35 degrees with the horizontal. His force is parallel to the slope. If the speed of the crate
decreases at a rate of 1.3m/s2, then the work done by the man is:
9. An ideal spring is hung vertically from the ceiling. When a 3 kg mass hangs at rest from it the spring
is extended 5 cm from its relaxed length. A downward external force is now applied to the hanging
mass to extend the spring an additional 8 cm. While the spring is extended by the external force,
the work done by the spring is:
10. A 2 kg crate falls from a height of 1.5m onto an industrial spring scale with a spring constant of 1.7 x
106N/m. At its greatest compression the reading on the scale is:
11. A projectile of mass 0.75 kg is fired with an initial speed of 12m/s at an angle of 58 degrees above
the horizontal. The Potential Energy of the projectile-Earth system when the projectile is at its
highest point is:
12. A 2kg block starts from rest on a rough incline that makes an angle of 30 degrees with the
horizontal. The coefficient of kinetic friction is 0.3. As the block goes 2.5m down the incline, the
Mechanical Energy of the Earth-block system changes by: