Physics
Name:
A> Statics
Forces Problem Set 1
1)
What is the tension in the string that supports
the 0.225 kg birdfeeder?
2)
Find the tension in each cable that supports the
625 N mailbag shown below.
3)
What is the mass of the stoplight shown below?
4)
Find weight of the cat burglar shown below if the
tension in the horizontal cable is 845 N.
6)
After a day of testing race cars, you decide to
take your own 1550 kg car onto the test track.
While moving down the track at 10.0 m/s, you
uniformly accelerate to 30.0 m/s in 10.0 s. What
is the average net force that is applied to the car
during this time?
B> Dynamics
5)
A 873 kg (1930 lb) dragster, starting from rest
attains a speed of 26.3 m/s (58.9 mph) in 0.59 s.
a) What is the average acceleration of the
dragster during this time interval?
b) What is the magnitude of the average net
force on the dragster during this time?
c) Assume that the driver has a mass of 68 kg.
What horizontal force does the seat exert on
the driver?
7)
A 65 kg swimmer jumps off a 10.0 m tower
a) What is the swimmer’s velocity on hitting the
water?
b) The swimmer comes to a stop 2.0 m below
the surface of the water. What is the net
force exerted by the water on the swimmer?
8)
A 4500 kg helicopter accelerates upward at 2.0
m/s2. What lift force is exerted by the air on the
propellers?
9)
A crane holds a wrecking ball that weighs
98,000 N.
a) What upward force does the crane exert on
the wrecking ball?
b) If the crane begins to move the wrecking ball
upward with an acceleration of 2.0 m/s2,
what force is the crane exerting on the
wrecking ball?
10) A force of 90.0 N is exerted straight up on a
stone that weighs 7.35 N.
a) What is the mass of the stone?
b) What is the net force acting on the stone?
c) What is the acceleration of the stone?
11) A rocket weighs 7840 N on the earth. The force
of propulsion is 10,440 N
a) What is the mass of the rocket?
b) What is the net force acting on the rocket?
c) What is the acceleration of the rocket?
d) Starting from rest, what is the velocity of the
rocket at the end of 10.0 s?
C> Friction
12) A sled of mass 50.0 kg is pulled along snow
covered flat ground. The coefficient of static
friction is 0.30. The coefficient of sliding friction
is 0.10.
a) How much does the sled weigh?
b) What force will be needed to start the sled
moving?
c) What force is needed to keep the sled
moving at a constant velocity?
14) A 225 kg block accelerates across the floor as
the result of an applied force of 1100 N to the
right. The sliding frictional force is 600N.
600 N
a)
b)
13) The engine of a car with a mass of 350 kg
applies a force of 14, 875 N. The coefficient of
sliding friction between the tires and the
pavement is 0.25.
a) What is the weight of the car?
b) What is the force of friction opposing the
motion of the car?
c) What is the net force acting on the car?
d) What is the acceleration of the car?
c)
225 kg
1100 N
What is the actual force causing the
acceleration?
What is the magnitude and direction of the
acceleration?
What is the coefficient of friction between
the block and the floor?
15) A boy exerts a 36 N horizontal force as he pulls
a 52 N sled across a cement sidewalk at 0.25
m/s. What is the coefficient of kinetic friction
between the sidewalk and the metal sled
runners?
16) Suppose the sled from problem 20 runs on
packed snow. The coefficient of friction is now
only 0.12. If a person weighing 650 N sits on
the sled, what force is needed to pull the sled
across the snow at constant speed?
225 kg
17) A 10.0 N force is applied at 20.0 above the
horizontal to a 2.5 kg brick to drag it across a
table. The coefficient of sliding (kinetic) friction
is 0.35.
a) What is the normal force acting on the brick?
b) What is the force of friction acting on the brick?
c) What is the acceleration of the brick?
Fa = 10.0 N
2.5 kg
Forces Problem Set 1 Answers:
A> Statics
1) 2.21 N
2) 1040 N; 3) 8.7 kg
829 N
4) 637 N
B> Dynamics:
5) (a) 45 m/s2 (b) 39000 N (c) 3100 N
10) (a) 0.75 kg
(b) 82.65 N up
6) 3100 N
7) a) 14 m/s (b) 3185 N
8) 53,000 N
9) (a) 98,000 N (b) 118,000 N
(c) 110.2 m/s2 up
11) (a) 800. kg
(b) 2600 N up
2
(c) 3.25 m/s up (d) 32.5 m/s
C> Friction Forces:
12) (a) 490 N (b) 147 N (c) 49 N
14) (a) 500 N (b) 2.2 m/s2 right (c) 0.27
17) (a) 21.1 N (b) 7.39 N (c) 0.804 m/s2
13) (a) 3430 N (b) 858 N (c) 14,017 N (c) 40.0 m/s2
15) 0.69
16) 84 N