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Physics 30 Lessons 1 to 16 Review

1. An aeroplane travels 1800 km at a speed of 1000 km/h. It then encounters a headwind

that slows it to 850 km/h for the next 2300 km. hat was the avera!e speed of the

plane for this trip" #$10 km/h%

2. A line&acker starts from rest and accelerates at a constant rate for 2.0 s to make a

tackle '.0 m awa(. hat was the acceleration and the speed when makin! the tackle"#3.5 m/s2) ' m/s%

3. A car travellin! 80 km/h decelerates at 1.5 m/s2. *alculate #a% the distance it !oes

&efore it stops) #&% the time it takes to stop) and #c% the distance it travels durin! the

first and third seconds. #1+0m) 15 s) 21.3 m) 18.3 m%

,. A helicopter is ascendin! verticall( with a speed of 8.0 m/s- at a hei!ht of 120m a&ove

the earth) a packa!e is dropped from a window. ow much time does it take for the

packa!e to reach the !round" #5.8 s%

5. A deliver( truck travels 8 &locks north) + &locks east) and 10 &locks south. hat is itsfinal displacement from the ori!in" #+.3 &locks 18o of %

+. An aeroplane is travellin! 1000 km/h in a direction 3'oeast of north. #a% ind the

components of the velocit( vector in the northerl( and easterl( directions. #&% ow far

north and how far east has the plane travelled after 2.0 h" #15$' km north) 1203 km

east%

'. A swimmer is capa&le of swimmin! 1.8 m/s in still water. #a% If she swims directl(

across a 200 m wide river whose current is 0.80 m/s) how far downstream will she

land" #&% At what upstream an!le must the swimmer aim if she is to arrive at a point

directl( across the stream" #8$m) 2+o%

8. A motor&oat whose speed in still water is $.5 km/h must aim at a 55oan!le upstream

in order to travel directl( across the stream. #a% hat is the speed of the current" #&%

hat is the resultant speed of the &oat with respect to the shore" #'.8 km/h) 5., km/h%

$. If a &oat is to cross a river directl( to the opposite side when the current is 12 km/h) at

what an!le upstream must the &oat head. he &oat4s speed in still water is 20 km/h.

#3'oupstream%

10. A 5000k! helicopter accelerates upwards at 0.50 m/s2while liftin! a 2000k! car. #a%

hat is the lift force exerted &( the air on the propellers" #&% hat is the tension in theca&le that connects car to helicopter" #'.2 x 10,6) 2.1 x 10,6%

11. ow much force is needed to accelerate a +.0! &ullet from rest to 500 m/s over a

distance of 0.'0 m"

#1100 6%

12. hat is the avera!e force exerted &( a shot putter on a '.0 k! shot if the shot is moved

throu!h a distance of 2.' m and is released with a speed of 1, m/s" #250 6%

13. hat is the acceleration of a freel( fallin! +5 k! sk(diver if air resistance exerts a

force of 250 6" #5.$+ m/s2%

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1,. wo masses) 1.0 k! and 3.2 k!. are suspended over a pulle(. Assumin! the pulle( is

massless and frictionless) calculate the acceleration of the s(stem and the tension in

the cord. #5.1 m/s2) 1,.$ 6%

15. A roller coaster reaches the top of the steepest hill with a speed of 1., m/s. It then

descends the hill which is at an avera!e an!le of ,5 oand is 50 m lon!. hat will its

speed &e when it reaches the &ottom" #2+ m/s%

1+. A wet &ar of soap slides freel( down a ramp 10 m lon! inclined at an an!le of 8o.

ow lon! does it take to reach the &ottom" 6e!lect friction. #3.8 s%

1'. A space explorer is movin! throu!h space far from an( planet or star and notices a lar!e

rock) taken as a specimen from an alien planet) floatin! around the ca&in of the ship.

hould the explorer push it !entl( or kick it toward the stora!e compartment" h("

18. xplain wh( a rope clim&er must pull downward on the rope in order to move upward.

7iscuss the force exerted &( the clim&er4s arms in relation to the wei!ht of the clim&er

durin! the various sta!es of each step9 up the rope.

1$. xplain the relationship &etween mass and wei!ht.

20. 7raw a force dia!ram showin! the wei!ht and normal forces on a laundr( &asket in

each of the followin! situations:

a. at rest on a hori;ontal surface

&. at rest on a ramp inclined 12< a&ove the hori;ontal

c. at rest on a ramp inclined 25< a&ove the hori;ontal

d. at rest on a ramp inclined ,5< a&ove the hori;ontal

21. If the &asket in item 22 has a mass of 5.5 k!) find the ma!nitude of the normal force for

the situations descri&ed in #a% throu!h #d%.

22. xplain how placin! an o&=ect on an inclined plane instead of on a hori;ontal surface

affects the forces actin! on the o&=ect.

23. A massive metal o&=ect on a rou!h metal surface ma( under!o contact weldin! to that

surface. 7iscuss how this affects the frictional forces that arise &etween o&=ect and

surface.

2,. Ima!ine an astronaut in space at the midpoint &etween two stars of e>ual mass. If all

other o&=ects are infinitel( far awa() how much does the astronaut wei!h" xplain (our

answer.

25. Althou!h the frictional force &etween two surfaces ma( decrease as the surfaces are

smoothed) it will increase if the surfaces are made extremel( smooth and flat. xplain.

2+. Anal(se the motion of a rock dropped in water in terms of its speed and acceleration.

Assume that a resistive force actin! on the rock increases as the velocit( increases.

2'. A sk( diver falls throu!h the air. As the speed of the sk( diver increases) what happens

to the sk( diver4s acceleration" hat is the acceleration when the sk( diver reaches

terminal speed"

28. A 2.00 k! &lock is in e>uili&rium on an incline of an!le 0? +0.0

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2$. A 5., k! &a! of !roceries is in e>uili&rium on an incline of an!le 0 ? 15uires a +50 6 hori;ontal force to

set it in motion. After the clock is in motion) a hori;ontal force of 5+0 6 keeps it

movin! with a constant speed. ind sand k&etween the clock and the floor. #0.'0)

0.+0%

31. A &ox slides down a 30.0< ramp with an acceleration of 1.20 m/s2. 7etermine the

coefficient of kinetic friction &etween the &ox and the ramp. #0.,3+%

32. A car is travellin! at 50.0 km/h on a flat hi!hwa(.

a. If the coefficient of friction &etween the road and the tires on a rain( da( is 0.100)

what is the minimum distance needed for the car to stop" #$8.5 m%

&. hat is the stoppin! distance when the surface is dr( and the coefficient of

friction is 0.+00" #1+., m%

33. A 3.00 k! &lock starts from rest at the top of a 30.0< incline and slides 2.00 m down theincline in 1.50 s.

a. ind the acceleration of the &lock. #1.'8 m/s2%

&. ind the coefficient of kinetic friction &etween the &lock and the incline. #0.3'%

c. ind the frictional force actin! on the &lock. #$., 6%

d. ind the speed of the &lock after it has slid a distance of 2.00 m. #2.+' m/s%

3,. A hocke( puck is hit on a fro;en lake and starts movin! with a speed of 12.0 m/s.

xactl( 5.00 s later) its speed is +.00 m/s.

a. hat is its avera!e acceleration" #1.2 m/s2%

&. hat is the avera!e value of the coefficient of kinetic friction &etween puck and

ice" #0.12%c. ow far does the puck travel durin! this 5.00 s interval" #,5 m%

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