Read the scenario.
A cyclist is riding his bike at a constant speed of 5 m/s, and experiences a frictional force between the bike and sidewalk of 100 N. The cyclist then changes his speed to 10 m/s.
What effect does this increase in speed have on the frictional force between the bike and sidewalk?
The frictional force between the bike and sidewalk stays the same because speed does not affect frictional force.
The frictional force increases, but does not double because although friction increases with increasing speed, it does not increase as fast.
The frictional force increases and approximately doubles because the frictional force is directly proportional to the speed of the bike.
needs to be one of the answers shown
The frictional force between the bike and sidewalk stays the same because speed does not affect frictional force.
A ball moves along a smooth metal surface while an identical ball moves along concrete.
Which surface exerts a smaller amount of frictional force on the ball?
Responses
The concrete surface exerts less frictional force on the ball because there are fewer bumps and irregularities on the concrete than there are on the metal.
The concrete surface exerts less frictional force on the ball because there are fewer bumps and irregularities on the concrete than there are on the metal.
The concrete and metal surfaces exert the same amount of frictional force on the ball because they are both solid surfaces.
The concrete and metal surfaces exert the same amount of frictional force on the ball because they are both solid surfaces.
Neither concrete nor metal exert any friction on the ball because these two surfaces never result in a frictional force on any object.
Neither concrete nor metal exert any friction on the ball because these two surfaces never result in a frictional force on any object.
The metal surface exerts less frictional force because there are fewer bumps and irregularities on it than there are on the concrete.
The metal surface exerts less frictional force because there are fewer bumps and irregularities on it than there are on the concrete.
Study the scenario.
An object is at rest. At five seconds, someone comes over and pushes the object forward with a force of 10 N. After it is pushed, the object is still at rest.
Which of the following choices describes how static equilibrium could have been achieved when the object was pushed?
Responses
A force of exactly 10 N was exerted straight down on the object, countering the normal force.
A force of exactly 10 N was exerted straight down on the object, countering the normal force.
A force greater than 10 N was exerted in a forward direction on the object at exactly five seconds so that the forces were balanced, and the object remained at rest.
A force greater than 10 N was exerted in a forward direction on the object at exactly five seconds so that the forces were balanced, and the object remained at rest.
A force greater than 10 N was exerted straight down on the object, countering the normal force.
A force greater than 10 N was exerted straight down on the object, countering the normal force.
A backward force of 10 N was exerted on the box at exactly five seconds so that the forces were balanced, and the object remained at rest.
A force greater than 10 N was exerted in a forward direction on the object at exactly five seconds so that the forces were balanced, and the object remained at rest.
Study the image of two people pushing on opposing sides of a dog house at the same time.
Two people pushing on a doghouse. Force vector arrows are marked 25 N upward and 25 N downward; 10 N to the left and 10 N to the right.
Modified by FlipSwitch.
vberla/Shutterstock
Compute the amount of force acting on the doghouse using the vector addition rule.
Responses
0 N, the doghouse remains at rest.
0 N, the doghouse remains at rest.
70 N, the doghouse remains at rest.
70 N, the doghouse remains at rest.
0 N, the doghouse starts moving in one direction and then slows to a stop.
0 N, the doghouse starts moving in one direction and then slows to a stop.
20 N, the doghouse remains at rest.
NEEDS TO BE ONE OF THE ANSWERS SHOWN!!!
70 N, the doghouse remains at rest.
A puck is sliding along a frictionless surface at constant velocity.
Which of the following choices correctly models the forces acting on the puck?
Responses
A puck with one force vector to the right: initial push (person on puck).
Arrows and labels added by FlipSwitch.
Cline, Dusty/Shutterstock
Image with alt text: A puck with one force vector to the right: initial push (person on puck). Arrows and labels added by FlipSwitch. Cline, Dusty/Shutterstock
A puck with three force vectors. Two are equal opposing forces: gravitational (Earth on puck) straight down, and normal force (surface on puck) straight up. An equal force of initial push (person on puck) points to the right.
Arrows and labels added by FlipSwitch.
Cline, Dusty/Shutterstock
Image with alt text: A puck with three force vectors. Two are equal opposing forces: gravitational (Earth on puck) straight down, and normal force (surface on puck) straight up. An equal force of initial push (person on puck) points to the right. Arrows and labels added by FlipSwitch. Cline, Dusty/Shutterstock
A puck with two equal force vectors: gravitational force (Earth on puck) straight down, and initial push (person on puck) to the right.
Arrows and labels added by FlipSwitch.
Cline, Dusty/Shutterstock
Image with alt text: A puck with two equal force vectors: gravitational force (Earth on puck) straight down, and initial push (person on puck) to the right. Arrows and labels added by FlipSwitch. Cline, Dusty/Shutterstock
A puck with two equal opposing forces. Normal force (surface on puck) points straight up, and gravitational force (Earth on puck) points straight down.
Arrows and labels added by FlipSwitch.
Cline, Dusty/Shutterstock