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FORCE CONCEPT WS – honors
1)
Two equal forces act on two different objects, one of which has a mass 10 times as large as the other. How
will their respective accelerations compare?
2)
An object moving horizontally across a table is observed to slow down.
a. Is there unbalanced force acting on the object? Explain.
b. Is the gravitational force involved in accelerating the object in this situation? Explain.
3)
A ball hangs from a string attached to the ceiling, as shown in the diagram.
a. What forces act on the ball?
b. What is the total force acting on the ball?
c.
4)
For each force listed in your answer to (a), what is the reaction force given by Newton's 3rd Law?
The acceleration due to gravity on Mars is approximately 1/3 of the value that it has near the earth's surface
a. If a ball is transported to Mars, will its mass change? Explain.
b. Will the weight of the ball change in this process? Explain.
5)
Suppose that a bullet is fired from a rifle out in space where there are no appreciable forces of gravity. Will
the bullet slow down as it gets farther away from the rifle? Explain.
6)
The engine of a car is internal to the car and therefore cannot push directly on the car in order to accelerate
it.
a. What external force on the car is actually responsible for its acceleration? Explain.
b. Why is it difficult to accelerate a car on an icy road?
7)
Two identical cans are filled with different substances: one with lead shot and the other with feathers. An
astronaut standing on the moon (where there is gravity but no air resistance) drops the cans.
a. Which can, if either, experiences the greater gravitational force? Explain.
b. Which can, if either, experiences the greater acceleration? Explain.
c.
8)
Which can, if either, would require the greater force to stop it after it has fallen a certain distance?
Explain.
A sprinter accelerates at the beginning of a race and then attempts to maintain maximum speed throughout
the rest of the race.
a. What external force is responsible for accelerating the runner at the beginning of the race? Explain how
this force is produced.
b. Once the runner reaches his maximum speed, is it necessary to continue pushing against the track in
order to maintain that velocity? Explain.
9)
When will terminal velocity be reached for a freefalling object? What will be the object’s motion after that
point?
10)
If you want to give an object a lower terminal velocity, what should you do to it?
11)
An object is moving and the air resistance on it is increasing. What does this tell you about its speed?
12)
A lead ball and an aluminum ball, each one inch in diameter, are released simultaneously and allowed to fall
to the earth. Which of these balls, if either, reaches the ground first? Explain.
13)
Two identical eagles are shot by two poachers at the same instant and fall to the ground. Eagle #1 falls with
its wings outstretched while eagle #2 falls with its wings tucked against its body. Which hits the ground first?
Explain.