Graphs
Forces & Kinematics
Friction
Ropes & Pulleys
Final Jeopardy
100
The graph at left shows the relationship between the mass of a number of rubber stoppers and their resulting weight on some far-off planet. The slope of the graph is a representation of the....
(A) mass of a stopper
(B) density of a stopper
(C) acceleration due to gravity
(D) number of stoppers for each unit of weight
(C) acceleration due to gravity
100
The diagram shows a granite block being slid at constant speed across a horizontal concrete floor by a force parallel to the floor. Which pair of quantities could be used to determine the coefficient of friction for the granite on the concrete?
a) Mass and speed of the block
b) Mass and normal force on the block
c) Frictional force and speed of the block
d) Frictional force and normal force on the block
e) Normal force and speed of the block
d) Frictional force and normal force on the block
100
Three blocks of masses 3m, 2m, and m are connected to strings A, B, and C as shown above. The blocks are pulled along a rough surface by a force of magnitude F exerted by string C. The coefficient of friction between each block and the surface is the same. Which string must be the strongest in order not to break?
a) string A
b) string B
c) string C
d) They must all be the same strength.
e) It is impossible to determine without knowing the coefficient of friction.
c) string C
200
A known mass hangs from a force sensor inside of an elevator. As the elevator moves from the bottom floor to the roof-level of a building, the upward force acting on the mass is recorded as a function of time in the graph shown. At what time does the object begin slowing down to a rest?
8 seconds
200
The diagrams below show three situations in which one or more blocks are set on a frictionless track. The frictionless track has an inclined section and a straight section. A pulley wheel separates these two sections. In Case 1, a 2 kg block is set at rest on the inclined section. Upon release, the 2 kg block has an acceleration of 6 m/s2. In Case 2, a 1 kg block is set on the inclined section and released from rest. What acceleration will the 1 kg block have as it slides down the incline?
6 m/s2
200
Two workers are sliding a 300 kg crate across the floor. One worker pushes forward on the crate with a force of 380 N while the other pulls in the same direction with a force of 350 N using a rope connected to the crate. Both forces are horizontal, and the crate slides with a constant speed. What is the crate’s coefficient of kinetic friction on the floor?
0.25
200
Two 4 kg blocks hang from a rope that passes over two frictionless pulleys, as shown in the figure. What is the tension in the horizontal portion of the rope if the blocks are not moving and the rope and the two pulleys have negligible mass?
40 N
300
A known mass hangs from a force sensor inside of an elevator. As the elevator moves from the bottom floor to the roof-level of a building, the upward force acting on the mass is recorded as a function of time in the graph shown. What is the mass of the object? Use g = 10 m/s2
0.5 kg
300
The diagrams below show three situations in which one or more blocks are set on a frictionless track. The frictionless track has an inclined section and a straight section. A pulley wheel separates these two sections. In Case 1, a 2 kg block is set at rest on the inclined section. Upon release, the 2 kg block has an acceleration of 6 m/s2. In Case 2, a 1 kg block is set on the inclined section and released from rest. After 0.5 s, how will the displacement of the 2 kg block in case 1 compare to that of the 1 kg block in case 2?
Equal
300
A 4000 kg truck is parked on a 7.0° slope. How big is the friction force on the truck?
4800 N
300
The diagram shows two blocks, one 3 kg and the other 2 kg, hanging connected to the same string that passes over an ideal pulley. What acceleration do the blocks have when released from rest?
2 m/s2
400
A known mass hangs from a force sensor inside of an elevator. As the elevator moves from the bottom floor to the roof-level of a building, the upward force acting on the mass is recorded as a function of time in the graph shown. What is the acceleration of the elevator as it leaves the ground floor?
2 m/s2
400
A small box is on a ramp tilted at an angle theta above the horizontal. The box may be subject to the following forces: frictional (f), gravitational (mg), pulling or pushing (Fp) and normal (N). In the following free-body diagrams for the box, the lengths of the vectors are proportional to the magnitudes of the forces. Which figure best represents the free-body diagram for the box if it is sliding down the ramp at constant speed?
Figure C
400
A 1000 kg car traveling at a speed of 40 m/s skids to a halt on wet concrete where μk = 0.60. How long are the skid marks?
140 m
400
The diagram shows a 12 kg block initially at rest on a frictionless table. The block is attached to a hanging 8 kg mass by a string that passes over a massless frictionless pulley. What acceleration does the block have when the hanging mass is released from rest?
4 m/s2
500
A known mass hangs from a force sensor inside of an elevator. As the elevator moves from the bottom floor to the roof-level of a building, the upward force acting on the mass is recorded as a function of time in the graph shown. What is the maximum speed attained by the elevator? Use g = 10 m/s2
4 m/s
500
The diagrams below show three situations in which one or more blocks are set on a frictionless track. The frictionless track has an inclined section and a straight section. A pulley wheel separates these two sections. In Case 1, a 2 kg block is set at rest on the inclined section. Upon release, the 2 kg block has an acceleration of 6 m/s2. In Case 2, a 1 kg block is set on the inclined section and released from rest. Calculate the final velocity of the 2 kg block in case 1 after 0.4 s .
2.4 m/s
500
A stubborn 120 kg pig sits down and refuses to move. To drag the pig to the barn, the exasperated farmer ties a rope around the pig and pulls with his maximum force of 800 N. The coefficients of friction between the pig and the ground are μs = 0.80 and μk = 0.50. Is the farmer able to move the pig?
No
500
The diagrams below show three situations in which one or more blocks are set on a frictionless track. The frictionless track has an inclined section and a straight section. A pulley wheel separates these two sections. In Case 1, a 2 kg block is set at rest on the inclined section. Upon release, the 2 kg block has an acceleration of 6 m/s2. In Case 2, a 1 kg block is set on the inclined section and released from rest. Calculate the acceleration of the blocks in case 3 the instant the 2 kg block is released.
4 m/s2
500
A known mass hangs from a force sensor inside of an elevator. As the elevator moves from the bottom floor to the roof-level of a building, the upward force acting on the mass is recorded as a function of time in the graph shown.
What is the approximate height of the building?
24 m