Physical Science - Exam 1
Which has greater kinetic energy, a car traveling at 30 km/h or a car of half the mass traveling at 40 km/h? (Calculate the kinetic energies of both objects then compare)
The 30 km/h car
Strange as it may seem, it is just as hard to accelerate a car on the Moon as it is to accelerate the same car on Earth. This is because the
mass of the car is independent of gravity
A falling object that has reached its terminal speed continues to gain
neither speed nor acceleration
A horse exerts 500 N of force on a heavy wagon. The wagon pulls back on the horse with an equal force. The wagon still accelerates because
nevertheless there is still an unbalanced force on the wagon
After a rock that is thrown straight up reaches the top of its path and is starting to fall back down, its acceleration is (neglect air resistance)
the same as it was at the top of its path
An object is raised above the ground gaining a certain amount of potential energy. If the same object is raised twice as high, it gains
twice as much potential energy
If you push an object just as far while applying twice the force, you do
twice times as much work
T/F: An Earth satellite is simply a projectile freely falling around the earth.
True
Disregarding air resistance, objects fall at constant
acceleration
Hang from a pair of gym rings and the upward support forces of the rings will always
add up to equal your weight
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared to the force the stops the car, the force needed to stop the truck is
greater
In each second of fall, the distance a freely falling object will fall is
increasing
Your weight is
the gravitational attraction between you and the earth
The attraction of a person's body toward the earth is called weight. The reaction to this force is
the person's body pulling on the earth
A 1 kg mass at the earth's surface weighs about
10 N
The gain in speed each second for a freely falling object is about
10-m/s
On the surface of Jupiter, where the acceleration due to gravity is about 3 times that of Earth, a 100 kg rock would have a weight of about
3000 N
A projectile is launched at an angle of 40 degrees above the horizontal and lands downrange. What other projection angle for the same speed would produce the same downrange distance (neglect air resistance)?
50 degrees
If a car increases its velocity from zero to 60 km/h in 10 s, its acceleration is
6 km/h/s
If an object falls with constant acceleration, the velocity of the object must
continually change by the same amount each second
Which has zero acceleration? An object:
- Moving at constant velocity - In mechanical equilibrium - At rest
Distinguish between velocity and acceleration.
- Velocity can be defined as the speed and direction an object is going or falling at. - Acceleration is simply the rate of change of an objects velocity.
You do work on a body when you lift it against gravity. How does this work relate to gravitational potential energy? If the lifted body is dropped, what becomes of this energy?
- When you are lifting a body the work you do is going to be stored as gravitational potential energy. If you drop the lifted body that potential energy becomes kinetic energy.
In the same direction, an object travels 8 m in the first second of travel, 8 m again during the second second of travel, and 8 m again during the third second. Its acceleration in meters per second is
0 m/s/s
An apple weighs 1 N. the magnitude of net force on the apple when it is in free fall is
1 N
A 10 kg brick and a 1 kg book are dropped in a vacuum (no air resistance). The force of gravity on the 10 kg brick is
10 times as much as the force on the 1 kg book
A 10 N block and a 1 N block lie on a horizontal frictionless table (no friction). To push them with equal acceleration, we would have to push with
10 times as much force on the heavier block
A 10 N falling object encounters 6 N of air resistance. The magnitude of the net force on the object is
4 N
A man weighing 800 N stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is
400 N
It takes 6 s for a stone to fall to the bottom of a mine shaft. How deep is the shaft?
About 180 m
Strictly speaking, why will an object in free fall not experience terminal velocity as it falls?
An object in free fall doesn't encounter any air resistance and is at the mercy of gravity. Because of this it will only gain acceleration as it falls instead of experiencing terminal velocity which would prevent it from getting faster.
An object weighs 30 N on Earth. A second object weighs 30 N on the Moon. Which has the greater mass?
The one on the Moon
The two measurements necessary for calculating average speed are
distance and time
One object has twice as much mass as another object, and also has twice as much
inertia
A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of
power
Compared with the mass of a certain object on Earth, the mass of the same object on the Moon is
the same
If you push an object with twice the work input for twice the time, your power input is
the same amount as for half the work in half the time