Physics Ch.4
two tennis balls fall through the air from a tall building. One of them is filled with lead pellets. The ball to reach the ground first is the
lead-filled ball
a ball thrown straight upward takes 10 seconds for its up and down round trip. Because of air resistance the time taken for the just to go up is
less than 5s
a kilogram is a measure of an objects
mass
What object has a zero acceleration?
moving at constant velocity, mechanical equilibrium and at rest
when you stand at rest with your left foot on one bathroom and your right foot on a similar scale each of the scales will
show readings that equal your weight
what horizontally applied force will accelerate a 400 kg crate at 1 m/s2 across a factory floor against a friction force half its weight
2400N
a sky diver weighs 500 N reaches a terminal velocity of 90 km/s the air resisrance on suzie is then
250 N
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 when taking off
2m/s2
a 2000 kg car experiences a breaking force of 10000 N and skids to a stop in 6 seconds. The speed of the car just before the brakes were applied was
30 m/s
a 500N parachutist opens his chute and experiences an air resistance force of 800N the net force on the parachutist is then
300 N upward
a 1000 kg automobile enters a freeway on-ramp at 20 m/s and accelerates uniformly up to 40 m.s in a time of 10 secs. How far does the automobile travel during that time?
300 m
if you are driving at 20 m/s and slam on your brakes and skid at .5g to a full stop the skidding time is about
shows readings that when added equal your weight
an astronaut on another planet drops a 1 kg rock from rest. The astronaut notices that the rock falls 2 meters straight down in one second. On this planet, how much does the rock weigh
4 N
The human body can withstand an acceleration of 10 g under certain conditions. What net force would produce this acceleration for a 50 kg person
5000 N
a 10 kg block with an inital velocity of 10 m/s slides 10 meteres across a horizontal surface and comes to rest. It takes the block 2 seconds to stop. The stopping force acting on the block is about
50N
an astronaut on another planet drops a 1kg rock from rest and find that it falls a vertical distance of 2.5 meters in one second on this planet the rock has a weight of
5N
a 10 n falliing object encounters 4 n of air resistance the net force on the object is
6 N
a sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases air resistance also increase when air resistance equals 200N the sacks acceleration becomes
0m/s2
an object with teice as much mass as another object has twice as much
1 kg
an object with as much mass as another object has twice as much
inertia
when a falling object has reached its terminal velocity its acceleration is
zero
whenever the net force of an object is zero its acceleration is
zero
a boulder following a straight line path at constant velocity has
zero acceleration
a 1 kg ball is thrown at 10 m/s straight upward. neglecting air resistance the net force hat acts on the stone when it is half way to the top of its path is about
10 N
a 1 kg mass at the earths surface weighs
10 N
a 10-N block and a 1-N block lie on a horizontal frictionless table. To import equal horizontal accelerations, we would have to push the heavier block with
10 times as much force
a push on a 1 kg brick accelerates it. Negelecting friction, equally accelerating a 10-kg brick requires
10 times as much force
a 10 kg brick and a 1 kg apple are dropped in a vacuum the force of gravity on the brick is
10 times more than the force on the apple
a 1kg rock that weighs 10N is thrown straight upward at 20m/s. Neglecting air resistance the net force that acts on it when it is half way to the top of the path is
10N
a rock is thrown vertically into the air. AT a the top of its path its acceleration is
10m/s2
a block is dragged with out acceleration in a straight line path across a level surface by a force of 6N what is the force of friction between the block and surface
6N
a constant net force on a rail road car produces constant
acceleration
Which has the greater mass?
an automible battery
neglecting friction, a small and large block of ice begin sliding down an incline together. the larger the block reaches the bottom
at the same time
a heavy ball hangs by a string, with a second string attached to its bottom a quick pull on the bottom string will break the
bottom string
a vehicle undergoes acceleration when it
changes speed, changes direction
a skydiver steps from a helicopter and falls for a few seconds until terminal velocity is reached. Thereafter, until he opens his parachute his acceleration
decreases
A large and smal person wish to parachute at equal terminal velocities. The larger person should
get a larger parachute to cover more area
a coconut and a bird's feather fall from a tree through the air to the below the force of air resistance is
greater on the coconut
a heavy blcok at rest is suspended by a vertical rope. when the block accelerates upward by the rope the rope tension is
greater than the weight
If the mass of a cart is quickly loaded to have twice the mass while a propelling force remains constant the carts acceleration
halves
a skydivers terminal velocity will be greatest if she falls
head first
a heavy rock and a light rock of the same size are falling through the air from a tall building the one that encounters the greatest air resistance is the
heavy rock
If a nonrotating object has no acceleration then we can say for certain that it is
in mechanical equilibrium
if an objects mass is decreasing while a constant force is applied to the object the acceleration
increases
a bowling ball and a baseball accelerate equally when falling in a vacuum because
the ratio of their weights to a mass is the same
Which of the following is a vector quatity?
velocity
