| Question Answer | how much work is done on a 100 kg crate that is hoisted 2m in a time of 4s 100 x 10N = 1000 x 2m = 2000j |
|---|
Which equation is most directly useful for solving a problem that asks for the distance a speeding vehicle skids in coming to a stop?
twice the kinetic energy. 4 times as far. Which of the following equations is most directly useful for solving a problem that asks for the distance a speeding vehicle skids in coming
to
a stop? 50 MJ.
When two identical cars one traveling twice as fast as the other brake to a stop the faster car will skid?
That is a car traveling 10 mi/hr may require 4 feet to skid to an abrupt halt; but a car going twice as fast – 20 mi/hr – would require four times the distance –
16 feet
to skid to a stop. A doubling of the speed results in a quadrupling of the stopping distance.
When a car is braked to a stop its kinetic energy is transformed to?
Friction braking is the most commonly used braking method in modern vehicles. It involves the conversion of kinetic energy to
thermal energy
by applying friction to the moving parts of a system. The friction force resists motion and in turn generates heat, eventually bringing the velocity to zero.
Do 100 J of work in 50’s and your power output is?
Do 100 J of work in 50 s and your power output is…
2 W
. If an object is raised twice as high, its potential energy will be… twice as much.
Where is the pendulum when it has minimum potential energy?
When the pendulum
is at the bottom of its trajectory
, its potential energy will also be at its minimum. This is because the height of the mass attached to the pendulum is lowest at this point.
How much further will a car skid if it is traveling at 100 km HR than the same car traveling at 50 km/hr and the same average braking force is applied?
How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s? The 100 km/s car will travel
4 times as far
because it has four times as much kinetic energy.
What is being transferred as you do work?
When you do work on an object, some of
your energy is transferred to the object
. You can think of work as the transfer of energy. In fact, both work and energy are measured in the same unit, the joule. … Energy can be transferred from the man to the ball, but the total amount of energy in the system does not change.
What happens when two cars collide?
Collisions between objects are governed by
laws of momentum and energy
. When a collision occurs in an isolated system, the total momentum of the system of objects is conserved. … In the collision between the two cars, total system momentum is conserved.
How much work must the brakes of a car supply to stop a car moving four times as fast?
A four times as fast car has
16 times
as much DE and will require 16 times as much work to stop, and 16 times as much stopping distance.
How long does it take the car to slide to a stop?
Since there is a 1 second delay (driver reaction time) in hitting your brakes (both recognition and reaction time is often 2 seconds), the total time to stop is
5.4 seconds to 6.4 seconds
.
How do I calculate kinetic energy?
In classical mechanics, kinetic energy (KE) is
equal to half of an object’s mass (1/2*m) multiplied by the velocity squared
. For example, if a an object with a mass of 10 kg (m = 10 kg) is moving at a velocity of 5 meters per second (v = 5 m/s), the kinetic energy is equal to 125 Joules, or (1/2 * 10 kg) * 5 m/s
2
.
What happened to the car’s original kinetic energy?
The original kinetic energy was
converted into thermal energy by the negative work of friction
.
What is the work done equation?
To express this concept mathematically, the work W is equal to the force f times the distance d, or W = fd. If the force is being exerted at an angle θ to the displacement, the work done is
W = fd cos θ
.
Can momenta cancel?
For any array of several objects, the total momentum is the sum of the individual momenta. There is a peculiarity, however, in that momentum is a vector, involving both the direction and the magnitude of motion, so that the
momenta of objects going in opposite directions can cancel to yield an overall sum of zero
.
How do you know if work is positive or negative?
Work can be either positive or negative: if
the force has a component in the same direction as the displacement of the object
, the force is doing positive work. If the force has a component in the direction opposite to the displacement, the force does negative work.
When Freddy Frog drops vertically from a tree?
Freddy frog drops vertically from a tree onto a horizontally moving skateboard. The skateboard slows. Give two reasons for the slowing, one in terms of a horizontal friction force between Freddy’s feet and the skateboard, and one in terms of momentum conservation.
Where does a pendulum have maximum potential energy?
The maximum potential energy is
at the extreme positions
and the maximum kinetic energy is at the mean position.
Which requires more work lifting a 50 kg sack a vertical distance of 2m?
Which requires more work- lifting a 50-kg sack a vertical distance of 2 m or lifting a 25-kg sack a vertical distance or 4 m? Both are the
same amount of work
because the force x distance is the same for each.
How does a pendulum work physics?
A pendulum consists of a mass (known as a bob) attached by a string to a pivot point. As the pendulum moves it sweeps out a circular arc, moving back and forth in a periodic fashion. …
The force of gravity acts in a downward direction
and does work upon the pendulum bob.
Where is the maximum speed of a pendulum?
A pendulum reaches its maximum speed
at its lowest point
, so if you know the starting height (the difference in height between the highest and lowest point in the pendulum’s swing), you can work out the maximum speed using kinetic and potential energy formulas.
What is the skid distance formula?
dis the distance the car skidded (in feet). fis a special number (called the coefficient of friction) that depends on the road surface and road conditions.
S = ~30d(I.O)
(dry tar road). For a wet tar road, f is about 0.5, so the formula is S = ~ 30d(0.5) (wet tar road).
What is the stopping distance for a car?
| Speed Perception/Reaction Distance Braking Distance | 40 mph 59 feet 80 feet | 50 mph 73 feet 125 feet | 60 mph 88 feet 180 feet | 70 mph 103 feet 245 feet |
|---|
What is the stopping distance of a vehicle?
Stopping distance is
the total distance you travel before you apply the brakes
, plus the distance you travel while the brakes slow you down. Thinking distance+ braking distance = overall stopping distance.
What is the rate of work done?
The SI unit of work done is joule. Now, the rate of work done means
the amount of work done per unit time
. Now, power can be defined as the amount of energy Transferred per unit time. Energy transferred is the same as the work done on the object.
What is the rate of doing work?
In physics,
power
is the rate of doing work. It is the amount of energy consumed per unit time. The unit of power is the joule per second (J/s), known as the watt (in honor of James Watt, the eighteenth-century developer of the steam engine).
How do you calculate speed after a collision?
If two particles are involved in an elastic collision, the velocity of the second particle after collision can be expressed as:
v2f=2⋅m1(m2+m1)v1i+(m2−m1)(m2+m1)v2i v 2 f = 2 ⋅ m 1
( m 2 + m 1 ) v 1 i + ( m 2 − m 1 ) ( m 2 + m 1 ) v 2 i .
What is collision formula?
An elastic collision is a collision where both the Kinetic Energy, KE, and momentum, p are conserved. In other words, it means that
KE
0
= KE
f
and p
o
= p
f
. Moreover, as p = linear momentum = mv, then we will write m
1
v
1i
+ m
2
v
2i
= m
1
v
1f
+ m
2
v
2f
. …
How much work is done when you push a crate horizontally with 100N?
If you push a crate horizontally with 100N across a 10m floor and the friction between the crate and floor is a steady 70N, how much kinetic energy does the crate gain? 12. ΔKE = work done =
(100 N – 70 N)(10 m)
= (30 N)(10 m) = 300 Nm = 300 J.
How do you calculate energy transferred?
Calculate energy transfer using
temperature change and the substance’s capacity for heat
. Determine the substance’s temperature rise. If a quantity of water, for instance, rises from 20 degrees Celsius to 41 degrees: 41 – 20 = 21 degrees. Multiply the result by the substance’s mass.
What happens when a bug hits the windshield?
Newton’s laws of motion require an equal and opposite force. The bug hits the windshield with
the same magnitude of force as
the windshield hits the bug, just in opposing directions.
How many times more work is required to stop the car now that it is going twice as fast?
A car moving at twice the speed of another has
four times
as much kinetic energy, and will require four times as much work to stop. The frictional force is nearly the same for both cars, so the faster one takes four times as much distance to stop.
Which requires more work lifting a 50 kg sack vertically 2 meters or lifting a 25 kg sack vertically 4 m?
Lifting the more massive car requires ____ work. The force required to raise the car at constant speed is equivalent to the weight (m*g) of the car. Since the 2400-kg car weighs 2X as much as the 1200-kg car, it would require twice as much work to lift it the same distance. 12.
Can a body have kinetic energy without momentum?
The body has zero momentum signifies that either the body has zero mass or the velocity of a body is zero. If either of the mass or velocity is zero, the kinetic energy (K = 12mv2 ) will be zero. Therefore,
it is not possible that a body has kinetic energy without
having momentum.
What happens to the kinetic energy of a car after you take your foot off the accelerator?
But when you decelerate by taking your foot off the throttle,
the electric motor stops supplying power so the vehicle will slow down
. When the motor stops, it immediately disengages, and then starts running backwards. … It captures the kinetic energy from the wheels as they slow down, and converts it into electricity.
How energy is transferred when vehicles stop?
When a car brakes, the total kinetic energy it had is
transferred into the heat energy from the friction of the brakes
and the heat energy of the friction of the grip of the tyre on the road. … The movement of the car ends in heat when the car brakes and stops.
Why you should drive slower at night?
Drive slower
One of the main reasons why you should drive slower at night is because
of slower reaction times
. With limited visibility, reacting to hazards, traffic signs, and other vehicles takes longer. By driving slower, you’ll have more time to make the appropriate actions when necessary.
How do you calculate braking and stopping distance?
- thinking distance = 12 m.
- braking distance = 24 m.
- total stopping distance = 36 m.
What reduces traction even more than rain?
Ice and snow
. Ice and snow reduce traction even more than rain. Traction is poorest near 32°F, when snow and ice start to melt and become a slippery, watery slush.
What is the formula of Ke?
Kinetic energy is directly proportional to the mass of the object and to the square of its velocity:
K.E. = 1/2 m v
2
. If the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of kilograms-meters squared per second squared.
