Phys 100 Wk 3: Newton's 2nd Law of Motion

An apple at rest weighs 1 N. The net force on the apple when it is in free fall is

1 N

The mass of a pet turtle that weighs 10 N is about

1 kg

A 10-kilogram block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. The acceleration of the block is

1 m/s2.

A 1-kg ball is thrown at 10 m/s straight upward. Neglecting air resistance, the net force that acts on the stone when it is halfway to the top of its path is about

10 N

A 1-kg mass at the Earth's surface weighs

10 N

A 1-kg rock that weighs 10 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

10 N

The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is

10 N.

A rock is thrown vertically into the air. At the top of its path, its acceleration is

10 m/s2.

A 10-N block and a 1-N block lie on a horizontal frictionless table. To impart 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. Neglecting 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 bag of groceries that has a mass of 10 kilograms weighs about

100 N

The mass of a lamb that weights 110 N is about

11 kg

An object released from rest on another planet requires one second to fall a distance of 6 meters. What is the acceleration due to gravity on this planet?

12 m/s2

A tow truck exerts a force of 3000 N on a car, which then accelerates at 2 m/s2. What is the mass of the car?

1500 kg

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?

2 m/s2

A car has a mass of 1000 kg and accelerates at 2 m/s2. What net force is 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 of the car?

220 m/s2

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?

2400 N

Nellie pulls on a 10-kg wagon with a constant horizontal force of 30 N. If there are no other horizontal forces, what is the wagon's acceleration?

3.0 m/s2

A 2000-kg car experiences a braking force of 10,000 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 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is then

300 N upward.

A 300-kg bear grasping a vertical tree slides down at constant velocity. The friction force between the tree and the bear is

3000 N.

If you are driving at 20 m/s and slam on your brakes and skid at 0.5g to a full stop, the skidding time is about

4 s

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?

4N

A mobile phone is pulled northward by a force of 10 N and at the same time pulled southward by another force of 15 N. The resultant force on the phone is

5 N

An astronaut on another planet drops a 1-kg rock from rest and finds that it falls a vertical distance of 2.5 meters in one second. On this planet, the rock has a weight of

5 N

Scotty Skydiver of mass 100 kg experiences air resistance of 500 N, and an acceleration of about

0.5 g

A 10-kilogram block with an initial velocity of 10 m/s slides 10 meters 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

50 N

Suzie Skydiver, who weighs 500 N, reaches terminal velocity of 90 km/h. The air resistance on Suzie is then

500 N

Phil stands at rest with both feet on a scale that reads 500 N. When he gently lifts one foot, the scale reads

500 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-N falling object encounters 4 N of air resistance. The net force on the object is

6 N

A block is dragged without acceleration in a straight-line path across a level surface by a force of 6 N. What is the force of friction between the block and the surface?

6 N

Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has the same

None of these

Neglecting friction, a small and a large block of ice begin sliding down an incline together. The larger block reaches the bottom

at the same time as the small block.

A coconut and a bird's feather fall from a tree through the air to the ground below. The force of air resistance is

greater on the coconut.

If the mass of a cart is quickly loaded to have twice the mass while a propelling force remains constant, the cart's acceleration

halves

A skydiver's terminal velocity will be greatest if she falls

head first.

Two objects of the same size, but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the

heavier object.

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 non-rotating object has no acceleration, then we can say for certain that it is

in mechanical equilibrium.

When the bottom string is pulled slowly in the heavy-ball-and-strings demonstration (Figure 4.8 in your book), tension

in the top string is due to your pull plus the weight of the ball.

If an object's mass is decreasing while a constant force is applied to the object, the acceleration

increases

Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has twice as much

inertia, volume, and mass.

An object with twice as much mass as another object has twice as much

inertia.

A heavy block at rest is suspended by a vertical rope. When the block accelerates upward by the rope, the rope tension

is greater than its weight.

If the net force on a cart is tripled, the cart's acceleration

is three times as much.

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

is zero

A single brick falls with acceleration g. The reason a double brick falls with the same acceleration is

its ratio of force to mass is the same.

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 is thrown vertically into the air. Because of air resistance, its speed when it returns to its starting level compared with its initial speed is

less

A ball thrown straight upward takes 10 seconds for its up-and-down round trip. Because of air resistance, the time taken for the ball just to go up is

less than 5s

A ball is thrown upwards and caught when it returns. Compared with its initial speed and in the presence of air resistance, the speed with which it is caught is always

less.

A kilogram is a measure of an object's

mass.

A rock is thrown vertically into the air. At the top of its path the net force on it is

mg

In which case would you have the largest mass of gold? If your chunk of gold weighed 1 N on the

moon

A ball is thrown vertically into the air. Because of air resistance, its time coming down compared to its time going up is

more

An object's weight is properly expressed in units of

newtons

A car by itself is capable of a certain maximum acceleration. When it tows a car of the same mass, its maximum acceleration is

one half

A car by itself is capable of a certain maximum acceleration. When it tows a twice-as-massive car, its maximum acceleration is

one third

When you stand at rest with your left foot on one bathroom scale and your right foot on a similar scale, each of the scales will

show readings that when added equal your weight.

If you double the net force on an object, you'll double its

speed

Two factors that greatly affect air resistance on falling objects are frontal area and

speed

Your weight as measured on your bathroom scale is

the force due to gravity on you.

A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to the ground first?

the heavy man

A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to a state of zero acceleration first?

the light woman

Strange as it may seem, it is just as difficult to accelerate a car on a level surface on the Moon as it is here on Earth because

the mass of the car is independent of gravity.

When a constant and sustained upward force acts on a rocket, its acceleration increases mainly because

the mass of the rocket decreases as fuel is burned.

A rock weighs 30 N on Earth and another rock weighs 30 N on the Moon. Which rock has the greater mass?

the one on the Moon

A feather and a coin will have equal accelerations when falling in a vacuum because

the ratio of both the feather's and coin's weight to mass is the same.

A bowling ball and a baseball accelerate equally when falling in a vacuum because

the ratio of their weights to mass is the same.

Compared to the mass of an apple on Earth, the mass of the apple on the Moon is

the same

The brakes of a speeding truck are slammed on and it skids to a stop. If the truck were heavily loaded so that it had twice the total mass, the skidding distance would be

the same

A force of 1 N accelerates 1-kg box at the rate of 1 m/s2. The acceleration of a 2-kg box by a net force of 2 N is

the same.

Recall Galileo's Leaning Tower experiment. With negligible air resistance, a heavy and a light object fall

to the ground in equal times, with the same increases in speed, and with equal accelerations.

A heavy ball hangs by a string, with a second string attached to its bottom. A slow pull on the bottom string breaks the

top string

When a falling object has reached its terminal velocity, its acceleration is

zero

Whenever the net force on an object is zero, its acceleration

zero

A boulder following a straight-line path at constant velocity has

zero acceleration

The force required to maintain a constant velocity for an astronaut in free space is equal to

zero.

If more horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object

accelerates in the direction of the applied force.

If an apple experiences a constant net force, it will have a constant

acceleration

A constant net force on a rail-road car produces constant

acceleration.

Which has the greater mass? (pillow or battery)

an automobile battery

At equilibrium on a bathroom weighting scale, the downward pull of gravity on you is balanced by

an upward support force

Which has zero acceleration? An object

at rest, moving at constant velocity, and in mechanical equilibrium

A 10-N falling object encounters 10 N of air resistance. The net force on the object is

0 N

An apple weighs 1 N. When the apple is held at rest above your head, the net force on the apple is

0 N

A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200 N, the sack's acceleration becomes

0 m/s2

A heavy ball hangs by a string, with a second string attached to its bottom (Figure 4.8 in your book). A quick pull on the bottom string breaks the

bottom string.

You drive your car at a constant 60 km/h along the highway. You apply the brakes until the car slows to 40 km/h. If at that moment you suddenly release the brakes, the car tends to

continue moving at 40 km/h.

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. The particle with both forces acting

continues at the speed it had when it encountered the second force.

Suzie Skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration

decreases

If less horizontal force is applied to a sliding object than is needed to maintain a constant velocity, the object

eventually slides to a stop

The newton is a unit of

force

A large and a small person wish to parachute at equal terminal velocities. The larger person should

get a larger parachute