P2.2 - Everything in the Specification

When a [blank_start]force[blank_end] moves an [blank_start]object[blank_end] through a [blank_start]distance[blank_end], [blank_start]energy[blank_end] is transferred and [blank_start]work is done[blank_end].

What is the unit of work?

Fill in the blanks to complete the passage. When [blank_start]meteors[blank_end] and [blank_start]space[blank_end] [blank_start]shuttles[blank_end] enter the atmosphere, they have a very [blank_start]high[blank_end] [blank_start]kinetic[blank_end] energy. Due to [blank_start]collisions[blank_end] with particles in the atmosphere, some of the [blank_start]kinetic[blank_end] energy is transferred to [blank_start]heat[blank_end] energy, and [blank_start]work[blank_end] is [blank_start]done[blank_end]. The temperatures become so [blank_start]high[blank_end] that most [blank_start]meteors[blank_end] burn up; but [blank_start]space[blank_end] [blank_start]shuttles[blank_end] have heat [blank_start]shields[blank_end] which prevent heat build-up and allow them to re-enter the atmosphere without burning up.

When an object is raised vertically, work is done against the force of gravity, and the object gains kinetic energy.

Earth's gravitational field strength is approximately...

[blank_start]POWER[blank_end] - The [blank_start]rate[blank_end] of doing work.

What does the kinetic energy of an object depend on?

Momentum is a vector.

The rule of [blank_start]conservation[blank_end] of [blank_start]momentum[blank_end] states that the [blank_start]total[blank_end] momentum [blank_start]before[blank_end] an event is [blank_start]equal[blank_end] to the momentum [blank_start]after[blank_end] an event.

A [blank_start]force[blank_end] causes a change in [blank_start]momentum[blank_end]. A larger [blank_start]force[blank_end] means a larger change in [blank_start]momentum[blank_end] (and so a greater [blank_start]acceleration[blank_end]). Similarly, if someone's [blank_start]momentum[blank_end] changes very quickly, the [blank_start]forces[blank_end] on the body will be large, and more likely to cause injury.

Give the two main examples of momentum in everyday life. Co[blank_start]llisions[blank_end] and exp[blank_start]losions[blank_end].

Fill in the blanks to complete the passage about regenerative brakes. Regenerative brakes are used in some [blank_start]electric[blank_end] or hybrid cars. They use the system that drives the vehicle to do the majority of the braking. Rather than converting [blank_start]kinetic[blank_end] energy into [blank_start]heat[blank_end] energy, they [blank_start]put the vehicle's motor into reverse[blank_end]. With the motor running backwards, the wheels are [blank_start]slowed[blank_end]. This also allows the motor to act as [blank_start]an electric generator[blank_end], converting [blank_start]kinetic[blank_end] energy into [blank_start]electrical[blank_end] energy, which is subsequently converted into [blank_start]chemical[blank_end] energy and stored in the vehicle's [blank_start]battery[blank_end]. This makes regenerative brakes far more efficient.

Complete the passage about safety in a car. [blank_start]CRUMPLE ZONES[blank_end] - Located at the [blank_start]front and back[blank_end] of the car, these [blank_start]crumple[blank_end] on impact. This means that the car's kinetic energy is converted into [blank_start]other forms of[blank_end] energy by the car body as it changes [blank_start]shape[blank_end]. Also [blank_start]crumple zones[blank_end] [blank_start]increase[blank_end] the impact time, [blank_start]decreasing[blank_end] the force produced by the change in [blank_start]momentum[blank_end]. [blank_start]SIDE IMPACT BARS[blank_end] - These are strong [blank_start]metal[blank_end] tubes fitted into car [blank_start]door panels[blank_end]. They help direct kinetic energy away from the passengers to other areas of the car, such as [blank_start]the crumple zones[blank_end]. [blank_start]SEAT BELTS[blank_end] - These [blank_start]stretch[blank_end] slightly, which increases the [blank_start]time taken[blank_end] for the wearer to stop. This decreases the [blank_start]forces[blank_end] that hit the individual's [blank_start]chest[blank_end]. Some of the kinetic energy is also [blank_start]absorbed[blank_end] by the seat belt stretching [blank_start]AIR BAGS[blank_end] - These also [blank_start]slow you down[blank_end] more gradually and prevent you from hitting [blank_start]hard surfaces[blank_end] inside the car..