Question 1

Two ice skaters push off against one another starting from rest. The 45.0-kg skater acquires a speed of 0.375 m/s. What speed does the 60.0-kg skater acquire? Assume no external forces act during the collision.

Accepted Answer

$$0.281\ \mathrm{m/s}$$

Question 2

A force acts on an object along the x-axis: $$F(x) = (2.00\ \mathrm{N/m})x + (1.00\ \mathrm{N/m^3$})x^3$. What is the change in potential energy as the object moves from x = 1.00$$\ \mathrm{m}$$ to x = 2.00$$\ \mathrm{m}$$?

Accepted Answer

$$-12.00\ \mathrm{J}$$

Question 3

A piece of thin uniform wire of mass $$m$$ and length $$3b is $$bent into an equilateral triangle. What is the moment of inertia of the wire triangle about an axis perpendicular to the plane of the triangle and passing through one of its vertices?

Accepted Answer

$$\frac{7}{12}mb^2$

Question 4

When a rigid body rotates about a fixed axis, all the points in the body have the same:

Accepted Answer

angular acceleration

Question 5

A machinist turns on a grinding wheel at rest. The wheel accelerates uniformly for $$10\ \mathrm{s} to$$ $$93\ \mathrm{rad/s}$$, runs at that speed for $$26\ \mathrm{s}$$, then decelerates uniformly at $$2.8\ \mathrm{$$rad/s^2$$}$$ until it stops. What is the time interval of angular deceleration?

Accepted Answer

$$37\ \mathrm{s}$$

Question 6

At which point is the magnitude of the force on the particle greatest, given the potential energy curve shown (points X, Y, Z)?

Accepted Answer

point X

Question 7

A 60-cm length of uniform wire, of 60 g mass, is bent into a right triangle with sides 24 cm, 10 cm, and 26 cm. What are the x and y coordinates of the center of mass, in cm?

Accepted Answer

$$(9, 4)$$

Question 8

Is it possible for a system to have negative gravitational potential energy?

Accepted Answer

Yes, since the choice of the zero of potential energy is arbitrary.

Question 9

Two stones, one of mass $$m$$ and the other of mass $$2m$$, are thrown upward with the same velocity from the same height. Which statement is true?

Accepted Answer

Both stones will reach the same height because they initially had the same amount of kinetic energy.

Question 10

A 15-g bullet is shot vertically into a 9-kg block and lifts it upward 6.0 mm before coming to rest. What is the initial kinetic energy of the bullet?

Accepted Answer

$$0.80\ \mathrm{J}$$

Question 11

A stationary $$1.67\ \mathrm{kg}$$ object is struck by a stick. The force is $$F = at - bt^2$, with a = 1500$$\ \mathrm{N/(ms)}$$, b = 20$$\ \mathrm{$$N/(ms^2$$)}$$, and t = 2.74$$\ \mathrm{ms}$$. What is the speed of the object just after it comes away from the stick?

Accepted Answer

$$3.7\ \mathrm{m/s}$$

Question 12

It requires $$6.0\ \mathrm{J} of $$work to push a $$2.0\ \mathrm{kg}$$ object from point $$A to$$ $$B up a $$frictionless ramp at $$30^\circ. $$What is the length $$s of $$the ramp?

Accepted Answer

$$0.90\ \mathrm{m}$$

Question 13

A $$1.15\ \mathrm{kg}$$ grinding wheel, $$22.0\ \mathrm{cm} in $$diameter, spins at $$20.0$$ revolutions per second. When power is turned off, it slows with constant angular acceleration and takes $$80.0\ \mathrm{s} to $$stop. What was the angular acceleration (in $$\mathrm{$$rad/s^2$$}$$)?

Accepted Answer

$$-0.016\ \mathrm{$$rad/s^2$$}$$

Question 14

Which of the following best describes the relationship between work and energy for a conservative force?

Accepted Answer

$$W = -\Delta U$$

Question 15

A ball is thrown straight up. At the highest point of its path, which of the following is true?

Accepted Answer

Its velocity is zero and its acceleration is downward.

Question 16

A disk and a ring, both with the same mass and radius, are released from rest at the top of an incline. Which reaches the bottom first and why?

Accepted Answer

The disk, because it has less rotational inertia.

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