Exam 2
An apple weighs 1 N. When held at rest above your head, the net force on the apple is
0
A falling skydiver of mass 100 kg experiences 500 N air resistance. The acceleration of the skydiver is
0.5 g
An apple at rest weighs 1 N. The net force on the apple when it is in free fall is
1 N
It takes 40 J to push a large box 4 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
10 N
A tow truck exerts a force of 3000 N on a car, accelerating it at 2 meters per second per second. What is the mass of the car?
1500 kg
A car moves 4 times as fast as another identical car. Compared to the slower car, the faster car has
16 times the KE.
A car moving at 50 km/hr skids 20 m with locked brakes. How far will the car skid with locked brakes if it were traveling at 150 km/hr?
180 m
A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. What is the jet's acceleration in meters per second per second when taking off?
2
Do 100 J of work in 50 s and your power output is
2 W
A 2 kg mass has 40 J of potential energy with respect to the ground. Approximately how high is it above the ground?
2 m
A car has a mass of 1000 kg and accelerates at 2 meters per second per second. What is the magnitude of the net force exerted on the car?
2000 N
A car traveling at 22 m/s comes to an abrupt halt in 0.1 second when it hits a tree. What is the deceleration in meters per second per second of the car?
220
A karate chop delivers a blow of 3000 N to a board that breaks. The force that acts on the hand during this event is
3000 N
A bow is drawn so that it has 40 J of potential energy. When fired, the arrow will ideally have a kinetic energy that is
40 J
Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed to do this job was
50 W
A skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on the diver is then
500 N
A diver who weighs 500 N steps off a diving board that is 10 m above the water. The diver hits the water with kinetic energy of
5000 J
A 10-N falling object encounters 4 N of air resistance. The net force on the object is
6 N
A 10.0 N force is pulling up on the ring of spring scale that weighs 2.0 N. If an 8.0 N mass is attached to the bottom hook of the scale, the scale reading would be
8.0 N
A 1-kg rock that weighs 9.8 N is thrown straight upward at 20 m/s. Neglecting air resistance, the net force that acts on it when it is half way to the top of its path is
9.8 N
If an object of constant mass experiences a constant net force, it will have a constant
acceleration.
If the mass of an object does not change, a constant net force on the object produces constant
acceleration.
Which has zero acceleration? An object
all of these
Strictly speaking, more fuel is consumed by your car if an air conditioner, headlights, or even a radio is turned on. This statement is
almost always true.
A hydraulic press, like an inclined plane, is capable of increasing energy.
always false
An archer shoots an arrow. Consider the action force to be exerted by the bowstring against the arrow. The reaction to this force is the
arrow's push against the bowstring.
Suppose a particle is being accelerated through space by a 10-N force. Suddenly the particle encounters a second force of 10 N in the opposite direction from the first force. The particle with both forces acting on it
continues at the speed it had when it encountered the second force.
A skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration
decreases
A car that travels twice as fast as another when braking to a stop will skid
four time as far
When a car is braked to a stop, its kinetic energy is transformed to
heat
If an object's mass is decreasing while a constant force is applied to the object, the acceleration
increases.
Wherever the is an action force, there must be a reaction force which
is exactly equal in magnitude.
The force exerted by the road on each tire of an accelerating car
is less than the combined force of all four tires on the road.
An object that has kinetic energy must be
moving
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.
If you push for a half hour or a whole hour against a stationary wall,
no work is done in either case.
A woman carries a heavy box across a room at a constant speed. How much work does she do on the box while walking ?
none
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
As a ball falls, the action force is the pull of the Earth's mass on the ball. The reaction force is the
pull of the ball's mass on the Earth.
A ball rolling down an incline has its maximum kinetic energy at
the bottom
A rocket becomes progressively easier to accelerate as it travels upward from the ground mainly because
the mass of the rocket decreases as fuel is burned.
Both A 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is
the same
An object is propelled along a straight-line path by a force. If the net force were doubled, the object's acceleration would be
twice as much.
If an object is raised twice as high, its potential energy will be
twice as much.
If you find that twice as much work is needed to perform a task but it takes twice as much time, the amount of power required is
unchanged
When a falling object has reached its terminal velocity, its acceleration is
zero