Conceptual Physics Ch 3

What is the average speed of a cheetah that sprints 100 meters in 4 seconds? If it sprints 50 meters in 2 seconds?

100m / 4s = 25 m/s 50m / 2s = 25 m/s

If a car increases its velocity from zero to 60 km/h in 10 seconds, its acceleration is A) 3 km/h/s. B) 6 km/h/s C) 600 km/h/s. D) 10 km/h/s. E) 60 km/h/s.

B) 6 km/h/s

If a gazelle travels 1 km at the rate of 100 km/hr, how long did it run? A) .01 hr. B) 10 hr. C) 1 hr. D) .1 hr.

A) .01 hr.

In free fall near the Earth's surface, if it takes an object 7 seconds to reach the ground,the total distance fallen is A) 245 m. B) 490 m. C) 35 m. D) 70 m.

A) 245 m.

A ball is thrown upwards and returns to the same position. Compared with its original speed after release, its speed when it returns is about A) the same. B) four times as much. C) half as much. D) twice as much

A) the same.

A car maintains a constant velocity of 100 km/hr for 10 seconds. During this interval its acceleration is A) zero. B) 110 km/hr. C) 1000 km/hr. D) 10 km/hr.

A) zero.

CG

Abbreviation for center of gravity.

mi

Abbreviation for mile.

acceleration due to gravity (g)

Acceleration of a freely falling object. Its value near Earth's surface is about 9.8 m/s each second.

average speed formula

Average speed = total distance / total time interval

If a ball rolling down an incline plane has an acceleration of 2 m/s2, after five seconds it has traveled A) 10 m. B) 25 m. C) 11 m. D) .2 m. E) 7 m.

B) 25 m.

While a car travels around a circular track at a constant speed, its A) inertia is zero. B) none of the above C) acceleration is zero. D) velocity is zero

B) none of the above

A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is A) equal to its weight divided by its mass. B) zero. C) equal to its weight. D) equal to the product of its mass times its weight.

B) zero.

If a turtle travels .01 m/s for 30 s, it has traveled a distance of A) .03 m B) 30 m. C) .3 m D) 3 m.

C) .3 m

If a ball rolling down an inclined plane has an acceleration of 2 m/s its velocity after 11 seconds is A) 11 m/s. B) 2 m/s. C) 22 m/s. D) .22 m/s. E) 5.5 m/s.

C) 22 m/s.

In free fall near the Earth's surface, if it takes an object 7 seconds to reach the ground, the speed at impact is A) 35 m/s. B) cannot be determined. C) 70 m/s. D) 7 m/s. E) 10 m/s.

C) 70 m/s.

Drop a rock from a 5-m height and it accelerates at 10 m/s2 and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of fall is about A) half as much. B) four times as much. C) the same amount. D) twice as much.

C) the same amount.

If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about A) a variable amount. B) 15 m/s. C) depends on its initial speed D) 10 m/s. E) 5 m/s.

D) 10 m/s.

The velocity changes in free fall by A) 7 m/s. B) 5 m. C) 10 m/s2. D) 10 m/s. E) 7 ft/s.

D) 10 m/s.

A car accelerates at 2 meters/s/s. Assuming the car starts from rest, how far will it travel in 10 s? A) 40 m B) 200 m C) 2 m D) 100 m E) 10 m

D) 100 m

If a greyhound runs 160 m in 10 s, its speed is A) less than 1 m/s. B) 1600 m/s. C) 10 m/s. D) 16 m/s.

D) 16 m/s.

In free fall near the Earth's surface, if it takes an object 7 seconds to reach the ground, its acceleration at impact is A) 49 m/s2. B) 5 m/s2. C) 70 m/s2. D) 7 m/s2. E) 10 m/s2.

E) 10 m/s2.

The two measurements necessary for calculating average speed are A) distance and acceleration B) velocity and time. C) acceleration and time. D) velocity and distance. E) distance and time.

E) distance and time.

During each consecutive second of fall, the distance a freely falling object will fall is A) about 15 m. B) none of these C) about 5 m D) about 10 m. E) increasing.

E) increasing.

In free fall, the distance fallen can be described as increasing with the square of the A) distance. B) average velocity. C) instantaneous velocity. D) acceleration. E) time.

E) time.

rate

How fast something happens or how much something changes per unit of time; a change in a quantity divided by the time it takes for the change to occur.

speed

How fast something moves; the distance an object travels per unit of time; the magnitude of velocity.

free fall

Motion under influence of gravity only.

telescope

Optical instrument that forms images of very distant objects.

average speed

Path distance divided by time interval.

vector quantity

Quantity in physics that has both magnitude and direction. Examples are force, velocity, acceleration, torque, and electric and magnetic fields.

scalar quantity

Quantity in physics, such as mass, volume, and time, that can be completely specified by its magnitude and has no direction.

acceleration (a)

Rate at which an object's velocity changes with time, which may be in magnitude (speed), direction or both.

speed formula

Speed = distance / time

instantaneous speed

Speed at any instant.

velocity

Speed of an object and its direction of motion; a vector quantity.

linear motion

Straight-line motion.

A hungry mosquito sees you resting in a hammock in a 3 m/s breeze. How fast and in what direction should the mosquito fly in order to hover above you for lunch?

The mosquito should fly towards you into the breeze. It should fly at 3 m/s to hover above you.

Total distance formula

Total distance = average speed x total time interval

In addition to the speedometer on a dashboard of every car is an odometer which records the distance traveled. If the initial reading is set at zero at the beginning of the trip and the reading is 40 km one-half hour later, a. what has been your average speed? b. Would it be possible to attain this average speed and never go faster than 80 km/h?

a. 40 km / .5 h = 80 km/h b. no - the trip starts and stops at rest which equals zero. The driver must travel at instantaneous speeds over 80 km/h at different time intervals to average 80 km/h. Average speeds are generally much lower than high instantaneous speeds.

If a car moves with an average speed of 60 km/h for an hour, it will travel a distance of 60 km. a. How far would it travel if it moved at this rate for 4 h? b. For 10 h?

a. 60 km/h x 4 h = 240 km b. 60 km/h x 10 h = 600 km

m

abbreviation for meter.