Question 1

A projectile is fired from ground level at an angle above the horizontal on an airless planet where $$g = 10.0\ \mathrm{m/s^2$}. $$The initial $$x$$ and $$y$$ components of its velocity are $$86.6\ \mathrm{m/s}$$ and $$50.0\ \mathrm{m/s}$$ respectively. How long after firing does it take before the projectile hits the level ground?

Accepted Answer

20.0 seconds

Question 2

A boy kicks a football with an initial velocity of $$20\ \mathrm{m/s} at an $$angle of $$25^	ext{o}$$ above the horizontal. If we neglect air resistance, what is the magnitude of the acceleration of the ball while it is in flight?

Accepted Answer

$$9.8\ \mathrm{m/s^2$}$$

Question 3

A person who normally weighs $$700\ \mathrm{N} is $$riding in an elevator that is moving upward but slowing down at a steady rate. If this person is standing on a bathroom scale inside the elevator, what would the scale read?

Accepted Answer

Less than $$700\ \mathrm{N}$$

Question 4

A car of mass $$1100\ \mathrm{kg} is $$traveling at $$27\ \mathrm{m/s}$$ and slows down to a complete stop in $$578\ \mathrm{m}. $$What is the magnitude of the average braking force acting on the car?

Accepted Answer

$$340\ \mathrm{N}$$

Question 5

The coefficients of static and kinetic friction between a $$3.0\ \mathrm{kg}$$ box and a horizontal desktop are $$0.40$$ and $$0.30$$, respectively. What is the force of friction on the box when a $$15\ \mathrm{N}$$ horizontal push is applied to the box?

Accepted Answer

$$12.0\ \mathrm{N}$$

Question 6

A flatbed truck is carrying a $$20\ \mathrm{kg}$$ crate up a sloping road. The coefficient of static friction between the crate and the bed is $$0.40$$, and the coefficient of kinetic friction is $$0.30. $$What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place?

Accepted Answer

$$22^	ext{o}$$

Question 7

Two displacement vectors of magnitudes $$21\ \mathrm{cm}$$ and $$79\ \mathrm{cm}$$ are added. Which one of the following is the only possible choice for the magnitude of the resultant?

Accepted Answer

$$37\ \mathrm{cm}$$

Question 8

Town A lies $$20\ \mathrm{km}$$ north of town B. Town C lies $$13\ \mathrm{km}$$ west of town A. A small plane flies directly from town B to town C. What is the displacement of the plane?

Accepted Answer

$$24\ \mathrm{km}$$, $$57^	ext{o}$$ north of west

Question 9

A force, $$\vec{F}_1$$, of magnitude $$2.0\ \mathrm{N}$$ and directed due east is exerted on an object. A second force exerted on the object is $$\vec{F}_2 = 2.0\ \mathrm{N}$$, due north. What is the magnitude and direction of a third force, $$\vec{F}_3$$, which must be exerted on the object so that the resultant force is zero?

Accepted Answer

$$2.8\ \mathrm{N}$$, $$45^	ext{o}$$ south of west

Question 10

A football is kicked at an angle $$	heta$$ with respect to the horizontal. Which one of the following statements best describes the acceleration of the football during its event if air resistance is neglected?

Accepted Answer

The acceleration is $$9.8\ \mathrm{m/s^2$} at $$all times.

Question 11

What is the magnitude of the horizontal component of the projectile's displacement at the end of $$2.0\ \mathrm{s}$$?

Accepted Answer

$$40\ \mathrm{m}$$

Question 12

A football is kicked with a speed of $$18\ \mathrm{m/s} at an $$angle of $$65^	ext{o} to $$the horizontal. How long is the football in the air? Neglect air resistance.

Accepted Answer

$$3.3\ \mathrm{s}$$

Question 13

How far does the football travel horizontally before it hits the ground?

Accepted Answer

$$38\ \mathrm{m}$$

Question 14

Refer to the velocity-time graph. Which statement is correct about the net force acting on the car during interval B?

Accepted Answer

Opposing forces may be acting on the car during interval B.

Question 15

A net force of $$25\ \mathrm{N} is $$applied for $$5.7\ \mathrm{s} to a$$ $$12\ \mathrm{kg}$$ box initially at rest. What is the speed of the box at the end of the $$5.7\ \mathrm{s}$$ interval?

Accepted Answer

$$12\ \mathrm{m/s}$$

Question 16

Two forces act on a $$4.5\ \mathrm{kg}$$ block resting on a frictionless surface as shown. What is the magnitude of the horizontal acceleration of the block?

Accepted Answer

$$1.8\ \mathrm{m/s^2$}$$

Question 17

During a push, an astronaut accelerates to the right with an acceleration of $$0.36\ \mathrm{m/s^2$}$$ and a total mass of $$1.0 	imes 10^4$\ \mathrm{kg}. $$What is the magnitude of the acceleration of the spacecraft?

Accepted Answer

$$0.36\ \mathrm{m/s^2$}$$

Question 18

A muscle builder holds the ends of a massless rope. At the center of the rope, a $$7.9\ \mathrm{kg}$$ ball is hung as shown. What is the tension in the rope if the angle $$	heta in $$the drawing is $$60^	ext{o}$$?

Accepted Answer

$$370\ \mathrm{N}$$

Fundamental Concepts in Introductory Physics: Kinematics, Dynamics, and Forces

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