Page 53 - Schaum's Outline of Theory and Problems of Applied Physics

38 MOTION IN A STRAIGHT LINE [CHAP. 3

(a) 15 m (c) 53 m
(b) 25 m (d )65 m

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3.8. A car with its brakes applied has an acceleration of −1.2 m/s . If its initial velocity is 10 m/s, the distance the car
covers in the first 5 s after the acceleration begins is
(a) 15 m (c) 35 m
(b) 32 m (d )47 m

3.9. The distance the car in Question 3.8 travels before it comes to a stop is
(a) 6.5 m (c) 21 m
(b) 8.3 m (d )42 m

Supplementary Problems

3.1. A ship steams at a constant velocity of 30 km/h. (a) How far does it travel in a day? (b) How long does it take to travel
500 km?

3.2. A car moves at 50 km/h for 1 h and then at 60 km/h for 2 h. (a) How far did it go? (b) What was its average velocity
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for the entire trip?
3.3. A woman jogs halfway home at 8 km/h and walks the rest of the way at 6 km/h. Find her average velocity for the
entire trip.

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3.4. An airplane whose airspeed is 500 km/h covers a distance of 1000 km in 2 h. How strong was the headwind against
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it?
3.5. A boat moving downstream (with the current) in a river takes 4 min7stocovera measured mile according to marks
on shore, and 7 min 30 s to cover the same distance moving upstream (against the current). If the boat’s velocity
relative to the water is 11 mi/h, what is the velocity of the current in the river?

3.6. How long does it take an echo to return to a woman standing 300 m from a cliff? The velocity of sound in air is about
343 m/s.

3.7. A car moving at 100 km/h is 80 km behind another car moving at 60 km/h in the same direction. How far does the
first car travel before it overtakes the second car?

3.8. A pitcher takes 0.1 s to throw a baseball, which leaves his hand at a velocity of 30 m/s. What is the acceleration of
the baseball while it is being thrown?

3.9. A car comes to a stop in 6 s from a velocity of 30 m/s. (a) What is its acceleration? (b) At the same acceleration, how
long would it take the car to come to a stop from a velocity of 40 m/s?

3.10. The brakes of a car can slow it down from 60 to 40 km/h in 2 s. How long will it take to bring the car to a stop from
an initial velocity of 25 km/h at the same acceleration?

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3.11. An object starts from rest with an acceleration of 10 m/s . (a) How far does it go in 0.5 s? (b) What is its velocity
after 0.5 s?
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3.12. A car has an initial velocity of 10 m/s when it begins to be accelerated at 2.5 m/s . (a) How long does it take to reach
a velocity of 25 m/s? (b) How far does it go during this period?

3.13. The brakes of a car moving at 14 m/s are applied, and the car comes to a stop in 4 s. How far does the car go while it
is slowing down from 14 to 10 m/s?