Mechanics | Relativity Answers

A racecar, traveling at constant speed, makes one lap around a circular track of radius r
in a time t. Determine the magnitude of the average velocity of the car for one complete
lap.

A 2-kg metal block slides on a rough horizontal surface inside an insulated box. After
sliding a distance of 500.0 m, its temperature increased by 2.00 0C. Assuming that all
heat generated by frictional heating goes into the metal block, and the metal has a
specific heat capacity of 0.150 cal/(g.0C), find:
(i) How much work (heat Q) does the force of friction does on the block?
(ii) What is the coefficient of kinetic friction between the block and the surface?

Uniform circular motion is a direct consequence of:
A. Newton’s 3rd law
B. force that is tangent to path
C. acceleration that is tangent to the path
D. a force of constant magnitude that is always directed away from the same fixed point
E. a force of constant magnitude that is always directed towards the same fixed point

The coefficient of kinetic friction:
A. is in the direction of the frictional force
B. is in the direction of the normal force
C. is the ratio of force to area
D. can have units of Newtons
E. is none of the above

A ball with a weight of 1.5N is thrown at an angle of 30o above the horizontal with an
initial speed of 12m/s. At its highest point, the net force on the ball is:

A. 9.8N, 30o below horizontal
B. zero
C. 9.8N, up
D. 9.8N, down
E. 1.5N, down

Acceleration is always in the direction:
A. of the displacement
B. of the initial velocity
C. of the final velocity
D. of the net force
E. opposite to the frictional force

Of the following situations, which one is impossible?
A. A body having velocity east and acceleration east
B. A body having velocity east and acceleration west
C. A body having zero velocity and non-zero acceleration
D. A body having constant acceleration and variable velocity
E. A body having constant velocity and variable acceleration

A box of mass 20 kg is being pulled across the floor with a constant velocity using a force
of 100 N acting at 30o above the horizontal. Calculate the coefficient of kinetic friction

A 6 kg box is held at rest by two ropes that form 30° angles with the vertical. An external
force F acts vertically downward on the box. The force exerted by each of the
two ropes is denoted by T. A force diagram, showing the four forces that act
on the box in equilibrium, is shown in the figure. The magnitude of force F is
410 N. What is the magnitude of force T.

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A patient lying at rest on an inclined bed starts to slide when the incline angle θ is to 17°.
What is the coefficient of static friction between the patient and the bed?
(Use g = 9.81 m/s2.)