Dynamics Problem Set
A> Statics:
1) Determine the normal force that is applied to the 110. kg skier shown below.
2) If the snow-covered surface in problem # 1 is frictionless, what force pulls the skier down the slope?
3) What is the tension in the string that supports the 225 g birdfeeder?
4) Find the tension in each cable that supports the 625 N mailbag shown below.
5) What is the mass of the stoplight shown below?
6) Find weight of the cat burglar shown below if the tension in the horizontal cable is 845 N.
7) What is the mass of the toy truck if the force of friction holding it in place is 18.5 N?
8) Its amateur night at the tightrope walker’s convention and a 600. N performer finds himself in the awkward position shown below. Find the tension the rope on either side of the performer.
9) A 200 N wagon and contents is to be pulled up a 15° incline at a constant speed. How large a force parallel to the incline is needed if friction effects are negligible?
10) Find the tension in the two wires that support the 100. N light fixture shown below.
11) If the tension in the wire supporting the bird feeder attached at 60° in 225 N, what is the tension in the wire attached at 30°?
12) A crate is held at rest on a frictionless 53° ramp by a rope parallel to the incline. If the tension in the rope is 7000. N, what is the mass of the crate?
13) What is the normal force acting on the sled if the child’s mass is 25.0 kg and his father applies a force of 100 N directed at 30° with the horizontal?
14) Instead of pushing, the father pulls on the sled with the same force at a 30° angle above the horizontal. What is the normal force in this situation?
15) If the sled is pulled at a constant speed across level ground, what is the force of friction in both of the situations in problems 13 & 14?
16) A street lamp weighs 150 N. It is supported by two wires that form an angle of 120° with each other. The tension in the wires is equal. What is the tension in each wire?
17) If the angle between the wires in problem #16 is reduced to 90.0°, what is the tension in each wire?
18) A 215 N box is placed on an inclined plane that makes an angle of 35.0° with the horizontal. Find the force of friction that holds the box on the incline.
19) Joe wishes to hang a sign weighing 750 N so that cable A attached to the store makes a 30.0° angle as shown below. Cable B is horizontal and attached to an adjoining building. What is the tension in cable B?
20) You pull your 18.0 kg suitcase at a constant speed on a horizontal floor by exerting a 43 N force on the handle. The force of friction on the suitcase is 27 N.
a) What angle does the handle make with the horizontal?
b) What is the normal force on the suitcase?
21) You push a 325 N trunk up a 20.0° inclined plane at a constant speed by exerting a 211 N force parallel to the plane’s surface.
a) What is the normal force acting on the trunk?
b) What is the sum of all of the forces acting on the trunk?
c) What is the magnitude and direction of the force of friction between the trunk and the plane’s surface?
B> Dynamics:
22) 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?
23) 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 force that you have applied to the car during this time?
24) 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?
25) A 4500 kg helicopter accelerates upward at 2.0 m/s2. What lift force is exerted by the air on the propellers?
26) A racecar with a mass of 700. kg starts from rest and travels 120 m in 2.0 s.
a) Ignoring frictional effects, what is the acceleration of the car?
b) What is the net force acting on the car?
27) 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?
28) A small rocket weighing 14.7 N is fired from a high platform but its engine fails to burn properly. The rocket gains an upward force of only 10.2 N. What is the rate of acceleration of the rocket?
29) 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?
30) 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:
31) 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?
32) 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?
33) 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.
a) What is the actual force causing the acceleration?
b) What is the magnitude and direction of the acceleration?
c) What is the coefficient of friction between the block and the floor?
34) 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?
35) Suppose the sled from problem 34 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?