PHYS 101 MIDTERM EXAM
A massive block is being pulled along a horizontal frictionless surface by a constant horizontal
force. The block must be __________.
- moving with a constant nonzero acceleration
Two forces, of magnitude 4N4N and 10N10N, are applied to an object. The relative direction of
the forces is unknown. The net force acting on the object __________.
- cannot have a magnitude equal to 5N
Select the correct equations that show that the acceleration of 5.0 m/s2 results from a net
force of 14 N exerted on a 2.8-kg cart.
- a=Fnet/m =14N/2.8kg =5.0m/s2
What is the net force acting on a 1-kgkg ball in free fall?
- 10N
What is the net force acting on a falling 1-kg ball if it encounters 2 N of air resistance?
- 8N
If the mass of a sliding block is tripled while a constant net force is applied, by how much does
the acceleration change?
- The acceleration is reduced to 1/3 of its original value.
State Newton's third law of motion.
- For every action there is an equal and opposite reaction.
The winner in a tug-of-war exerts the greatest force on
,- the ground
A boxer can hit a heavy bag with great force. Why can't he hit a piece of tissue paper in midair
with the same amount of force?
- The boxer can only hit the tissue paper with a force as large as the tissue paper can exert on
the boxer, and the low-mass tissue can only exert a weak force.
How many forces are required for an interaction?
- Two forces, an action and a reaction, are needed for an interaction.
Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action
force, identify the reaction force.
- The reaction force is the force by the ball on the bat.
Identify the force that propels a rocket.
- The rocket is propelled by the reaction force from the particles accelerated out the rear by
an action force from the rocket.
Can you physically touch a person without that person touching you with the same amount of
force?
- No, when you touch a person, they must touch you with an equal and opposite force.
Which has a greater momentum: a heavy truck at rest or a moving skateboard?
- The moving skateboard.
An impulse can be increased by
- increasing the force or increasing the time interval.
, For the same force, why does a long cannon impart more speed to a cannonball than a short
cannon?
- The force is applied for a longer time in the long cannon.
What is the momentum of an 9.0-kg bowling ball rolling at 3.0 m/s?
- p=27 kg⋅m/s
What impulse occurs when an average force of 8.0 N is exerted on a cart for 2.6 ?
- p=21 kg*m/s
In which is momentum conserved: an elastic collision or an inelastic collision?
- Momentum is conserved in elastic and inelastic collisions.
The work that is done when twice the load is lifted twice the distance is _______.
- four times as much.
What is the unit of work?
- Joule
When one does twice the work in twice the time, the power expended is _______.
- the same
The power required to exert 4-N force over 3 meters in 2 seconds is
-6W
Two cars are raised to the same elevation on service-station lifts. If one car is twice as massive
as the other, compare their gains of potential energy.
A massive block is being pulled along a horizontal frictionless surface by a constant horizontal
force. The block must be __________.
- moving with a constant nonzero acceleration
Two forces, of magnitude 4N4N and 10N10N, are applied to an object. The relative direction of
the forces is unknown. The net force acting on the object __________.
- cannot have a magnitude equal to 5N
Select the correct equations that show that the acceleration of 5.0 m/s2 results from a net
force of 14 N exerted on a 2.8-kg cart.
- a=Fnet/m =14N/2.8kg =5.0m/s2
What is the net force acting on a 1-kgkg ball in free fall?
- 10N
What is the net force acting on a falling 1-kg ball if it encounters 2 N of air resistance?
- 8N
If the mass of a sliding block is tripled while a constant net force is applied, by how much does
the acceleration change?
- The acceleration is reduced to 1/3 of its original value.
State Newton's third law of motion.
- For every action there is an equal and opposite reaction.
The winner in a tug-of-war exerts the greatest force on
,- the ground
A boxer can hit a heavy bag with great force. Why can't he hit a piece of tissue paper in midair
with the same amount of force?
- The boxer can only hit the tissue paper with a force as large as the tissue paper can exert on
the boxer, and the low-mass tissue can only exert a weak force.
How many forces are required for an interaction?
- Two forces, an action and a reaction, are needed for an interaction.
Consider hitting a baseball with a bat. If we call the force on the bat against the ball the action
force, identify the reaction force.
- The reaction force is the force by the ball on the bat.
Identify the force that propels a rocket.
- The rocket is propelled by the reaction force from the particles accelerated out the rear by
an action force from the rocket.
Can you physically touch a person without that person touching you with the same amount of
force?
- No, when you touch a person, they must touch you with an equal and opposite force.
Which has a greater momentum: a heavy truck at rest or a moving skateboard?
- The moving skateboard.
An impulse can be increased by
- increasing the force or increasing the time interval.
, For the same force, why does a long cannon impart more speed to a cannonball than a short
cannon?
- The force is applied for a longer time in the long cannon.
What is the momentum of an 9.0-kg bowling ball rolling at 3.0 m/s?
- p=27 kg⋅m/s
What impulse occurs when an average force of 8.0 N is exerted on a cart for 2.6 ?
- p=21 kg*m/s
In which is momentum conserved: an elastic collision or an inelastic collision?
- Momentum is conserved in elastic and inelastic collisions.
The work that is done when twice the load is lifted twice the distance is _______.
- four times as much.
What is the unit of work?
- Joule
When one does twice the work in twice the time, the power expended is _______.
- the same
The power required to exert 4-N force over 3 meters in 2 seconds is
-6W
Two cars are raised to the same elevation on service-station lifts. If one car is twice as massive
as the other, compare their gains of potential energy.
