Test 2
The watt, the unit of power, is equal to the
(volt)(ampere).
A 2-kg book is held 1 m above the floor for 50 s. The work done is
0.
A 100-kg astronaut ejects 4 g of gas from her propulsion pistol at a speed of 50 m/s. Her recoil speed is
0.2 mm/s.
A horse has a power output of 1 hp (746 W) when it is pulling a cart. If the cart covers 100 m in 30 s, the force the horse exerts on the cart is
0.22 kN.
The work you do in raising an orange from your waist to your mouth is roughly
1 J.
A 1-kg mass has a KE of 1 J when its speed is
1.4 m/s.
A 90-kg llama has an average power output of 80 W. The minimum time the llama can go up a hill 500 m high is
1.5 h.
A weightlifter raises a 200-kg barbell through a height of 2 m in 2.2 s. The average power he develops during the lift is
1.78 kW.
The mechanical advantage of a pair of scissors might be
1/2.
A total of 4900 J is expended in lifting a 50-kg mass. The mass is raised to a height of
10 m
The KE of a 900-kg car whose speed is 60 km/h is
125 kJ.
A 1-kg object is moving at 10 m/s. To double its kinetic energy, its speed should be increased to approximately
14 m/s.
A horizontal force is applied to a 2-kg ball on a smooth table. The ball's speed is 8 m/s when it has gone 4 m. The magnitude of the force is
16 N
The minimum force that must be applied to a machine with a mechanical advantage of 5 in order to lift a 100-kg crate is
196 N.
A 40-kg boy climbs a vertical ladder at 0.5 m/s. His power output is
196 W.
A ball whose momentum is mv strikes a wall and bounces off. The change in the ball's momentum is
2 mv
Two 240-watt light bulbs are connected in parallel across a 120-V power line. The current in each bulb is
2.0 A.
A charge of +Q attracts a charge of -Q 1 cm away with a force of F. Another charge of +Q is placed next to the first one. The force on the charge of -Q is now
2F
The primary coil of a transformer has 200 turns and its secondary coil has 50 turns, and the current in the secondary coil is 40 A. When a 12-V alternating current is applied to the primary coil of the transformer, the secondary voltage will be
3 V.
When a ton of coal burns, it loses 3.3 × 10-7 kg of mass. The energy given off is
3.0 × 1010 J.
The speed of a 1000-kg car whose KE is 450 kJ is
30 m/s.
The 2.5-kg head of an ax exerts a force of 80 kN as it penetrates 18 mm into the trunk of a tree. The speed of the ax head when it strikes the tree is
34 m/s.
A 1-N weight has a KE of 1 J when its speed is
4.4 m/s
A 150-kg safe on frictionless casters is being raised 1.20 m to the bed of a truck using planks 4.00 m long. The force needed to push the safe up is
441 N
The primary coil of a transformer has 200 turns and its secondary coil has 40 turns. If the current in the secondary coil is 25 A, the current in the primary coil is
5 A.
An 800-kg car moving at 80 km/h overtakes a 1200-kg car moving at 40 km/h in the same direction. If the two cars stick together, the wreckage has an initial speed of
56 km/h.
Six kJ of work is used to lift an object to a height of 100 m. The object's approximate mass is
6 kg.
The mass equivalent of 6.0 MJ is
6.7 × 10^-11 kg.
A sedentary person requires about 6 million J of energy per day. This rate of energy consumption is equivalent to about
70 W.
An 800-kg car moving at 80 km/h collides head-on with a 1200-kg car moving at 40 km/h in the opposite direction. If they stick together, the wreckage now has an initial speed of
8 km/h.
The voltage needed to produce a current of 8 A in a resistance of 12 ohms is
96 V.
According to the general theory of relativity, gravitation
is a distortion in space-time.
Protons and electrons have different masses. When they are the same distance apart, the electric force between two electrons
is the same as the force between two protons.
When the speed of an object is doubled,
its momentum is doubled
If a shell fired from a cannon explodes in midair,
its total KE increases.
Which of the following is (are) not a unit of power?
joule-second
An object that has linear momentum must also have
kinetic energy
If a spaceship 100 m long when at rest on the earth were to travel at nine-tenths the speed of light, its length as measured by an observer on the earth would be
less than 100 m.
In the formula E0 = mc2, the symbol c represents the speed of
light.
At different places on the earth's surface, the earth's magnetic field
may be different in both magnitude and direction.
The current with which a transformer is used
must be ac
A current-carrying loop in a magnetic field always tends to turn until the plane of the loop is
parallel to the field.
A moving object does not necessarily have
potential energy
The watt is a unit of
power
A positive electric charge
repels other positive charges
An atom consists of a
small positive nucleus surrounded at a distance by electrons.
A golf ball and a ping-pong ball are dropped in a vacuum chamber. When they have fallen halfway down, they have the same
speed
When a rubber rod is stroked with a piece of fur,
the rod becomes negatively charged and the fur becomes positively charged.
Two charges of +Q are 1 cm apart. If one of the charges is replaced by a charge of -Q, the magnitude of the force between them is
the same.
Which of the following quantities is always the same to all observers?
the speed of light in free space
What never changes when two or more objects collide is
the total momentum of all the objects.
Relative to the electric force between two protons, the gravitational force between them is
weaker.
Direct electric current cannot be used to operate
Transformers
A magnetic field does not interact with a
a stationary electric charge
The height above the ground of a child on a swing varies from 0.5 m at the lowest point to 2.0 m at the highest point. The maximum speed of the child is
about 5.4 m/s.
To prevent it from tumbling in flight, a projectile such as a football is sent off spinning. The physical principle involved is
conservation of angular momentum.
The conventional unit of battery capacity is the ampere-hour, which is actually a unit of
electric charge.
The particle easiest to remove from an atom is an
electron
Superconductors
have no electrical resistance.
The sun
attracts light waves passing nearby.