Work And Power

Question 1

What is the work done?

Answer 1

The work done is the amount of energy transferred, whenever a resultant force moves a body in the direction of the force.

Question 2

How do forces transfer energy?

Answer 2

Mechanically

Question 3

What does a force overcome?

Answer 3

An opposing force (eg. friction or air resistance)

Question 4

Calculating work done

Answer 4

More energy is transferred if the force is increased, as the object moves a greater distance.

Question 5

Work done formula

Answer 5

Work done (J) = Force (N) x Distance (m)

Question 6

How do you lift an object?

Answer 6

To lift an object, you must apply a minimum force that equals (balances) the weight.

Question 7

Weight formula

Answer 7

Weight (N) = mass (kg) x gravitational field strength (N/kg)

Question 8

Gravitational field strength on Earth

Answer 8

~9.8 N/kg

Question 9

Gravitational acceleration on Earth

Answer 9

~9.8 m/s^2

Question 10

What is a powerful person scientifically?

Answer 10

In the scientific sense of transferring energy, a powerful person or device can do a lot of work in a short space of time.

Question 11

What is power?

Answer 11

Power is the amount of energy transferred each second (or the rate of energy transferred).

Question 12

Power formula

Answer 12

Power (W) = Energy Transferred (J) / Time (s) = Work Done / Time
P = E/T or W/T

Question 13

What is the unit of power?

Answer 13

Watts (W), where W is the number of Joules (J) transferred per second

Question 14

Electric cooker

Answer 14

As you change the controls on an electric cooker, the electrical power of the heating element changes. The higher the power, the hotter the ring gets. This is because more energy is bering transferred by electric current into thermal energy of the ring each second.

Question 15

Car power

Answer 15

The most powerful car transfers more chemical energy (in the fuel) into kinetic energy per second. This means it can accelerate more rapidly to a higher speed.

Question 16

Power of an energy saving light bulb

Answer 16

20W

Question 17

Power of a normal light bulb

Answer 17

100W

Question 18

Power of a human

Answer 18

100W

Question 19

Power of a horse

Answer 19

736W

Question 20

Power of a kettle

Answer 20

3kW

Question 21

Power of a power station

Answer 21

850MW

Question 22

Gravitational Field Strength

Answer 22

The gravitational field strength at Earth’s surface produces a force of approximately 10N for every 1kg of mass. On heavier planets, like Jupiter, gravity is greater. Hence, the gravitational potential energy gained would also be greater for the same change in height.

Question 23

GPE formula

Answer 23

Change in GPE (J) = mass (kg) x gravitational field strength (N/kg) x change in height above ground (m)

ΔE = mgΔh

However, sometimes, there is no GPE.

Question 24

What is 1GJ?

Answer 24

1 billion J

Question 25

What is 1kJ?

Answer 25

1 thousand J

Question 26

What is kinetic energy?

Answer 26

Kinetic energy is the energy stored in an object’s movement.

Question 27

What is kinetic energy?

Answer 27

Kinetic energy is the energy stored in an object’s movement.

Question 28

Kinetic energy formula

Answer 28

Kinetic energy (J) = 1/2 x mass (kg) x velocity^2 (m/s)
E(k) = 1/2(m)(v^2)

m = 2E(k) / v^2

v = root(2E(k) / m)