Question 1

A croquet ball is hit with two forces: $$\vec{F}_1 = 10$$ units, $$18^\circ$$ north of east, and $$\vec{F}_2 = 10$$ units, $$18^\circ$$ east of north. What is the magnitude of the resultant force?

Accepted Answer

$$\approx 18.6$$

Question 2

A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of $$8.0\ \mathrm{m/s} at an $$angle of $$20^\circ$$ below the horizontal. It strikes the ground $$3.0\ \mathrm{s}$$ later. Find the height from which the ball was thrown.

Accepted Answer

$$39\ \mathrm{m}$$

Question 3

A truck on a straight road starts from rest, accelerating at $$2.0\ \mathrm{m/s^2$}$$ until it reaches a speed of $$20\ \mathrm{m/s}$$, then travels at this speed, stopping at a red light in $$15\ \mathrm{m}. $$The time taken to travel $$35\ \mathrm{m} is$$:

Accepted Answer

$$8.5\ \mathrm{s}$$

Question 4

A person stands on a scale in an elevator. As the elevator starts, the scale has a constant reading of $$391\ \mathrm{N}. As $$the elevator later stops, the scale reading is $$391\ \mathrm{N}. $$The magnitude of the acceleration is determined to be $$3.5\ \mathrm{m/s^2$}$$ upward. Determine the person's mass (in kg).

Accepted Answer

$$45.5$$

Question 5

Two blocks of mass $$3.5\ \mathrm{kg}$$ and $$5.0\ \mathrm{kg}$$ are connected by a massless pulley. The incline is frictionless. If the heavier block moves up the incline at $$2.0\ \mathrm{m/s^2$}$$, what is the acceleration of the lighter block?

Accepted Answer

$$2.3\ \mathrm{m/s^2$}$$

Question 6

A ball slides without friction down a loop-the-loop. If the ball is released from rest at a height $$h$$ above the bottom of the loop, what is its speed at the bottom?

Accepted Answer

$$\sqrt{2gh}$$

Question 7

A particle moves at constant speed in a circular path. Which statement about the acceleration vector is correct?

Accepted Answer

It points toward the center of the circle

Question 8

A wheel of radius $$2\ \mathrm{cm}$$ has an angular velocity of $$5\ \mathrm{rad/s}. $$What is the linear speed of a point on its rim?

Accepted Answer

$$0.1\ \mathrm{m/s}$$

Question 9

The center of mass of Earth's atmosphere is:

Accepted Answer

Near the surface of Earth

Question 10

A $$1.8\ \mathrm{kg}$$ block is resting at the top of a $$37^\circ$$ slope of height $$1.0\ \mathrm{m}. It is $$attached to a cylindrical pulley of mass $$1.7\ \mathrm{kg}$$ and radius $$0.35\ \mathrm{m} by a $$massless string that winds on the block slides downhill. If the acceleration of the block is $$1.9\ \mathrm{m/s^2$}$$, what is $$g$$?

Accepted Answer

$$10.4\ \mathrm{m/s^2$}$$

Question 11

Find the net torque on the wheel in Figure about the axle through $$O if$$ $$F_1 = 10.0$$\ \mathrm{N}$$ and F_2$ = 25.0\ \mathrm{N}.$$

Accepted Answer

$$3.45\ \mathrm{N \cdot m}$$

Question 12

A clock's second hand has an angular velocity of $$\omega = 0.105\ \mathrm{rad/s}. $$When it has made 10 revolutions, what is its angular displacement?

Accepted Answer

$$20\pi\ \mathrm{rad}$$

Question 13

Which of the following best describes the center of mass of a uniform solid sphere?

Accepted Answer

At the geometric center

Question 14

A ventilation fan with a moment of inertia $$I$$ has a kinetic energy $$K$$ due to its rotation. If its angular speed is halved, what kinetic energy does it have?

Accepted Answer

$$K/4$$

Question 15

A rotating flywheel can be stopped in $$2.0\ \mathrm{s} by $$applying a torque of $$25\ \mathrm{N \cdot m}. If $$its initial angular velocity is $$50\ \mathrm{rad/s}$$, what moment of inertia ($$I) $$does it have?

Accepted Answer

$$125\ \mathrm{kg \cdot m^2$}$$

Physics I Final Exam: Key Concepts and Problem Solutions

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