Mechanics

Question 1

Define acceleration.

Answer 1

The rate of change of velocity, a vector quantity.

Question 2

Define braking distance.

Answer 2

The distancec travelled by a vehicle from the time when the breaks are applied to when the vehicle stops.

Question 3

Define centre of gravity.

Answer 3

An imaginary point at which the entire weight of an object appears to act.

Question 4

Define centre of mass.

Answer 4

A point through which any externally applied force produces straight-line
motion but no rotation.

Question 5

Define closed system.

Answer 5

An isolated system that has no interaction with its surroundings.

Question 6

Define displacement.

Answer 6

The distance travelled in a particular direction, a vector quentity.

Question 7

Define drag force.

Answer 7

The resistive force exerted by a fluid on an object moving through it.

Question 8

Define energy.

Answer 8

The capacity for doing work, a scalar quantity.

Question 9

Define equilibrium.

Answer 9

A body is in equilibrium when the net force and net moment acting on it are zero.

Question 10

Define free fall.

Answer 10

The motion of an object accelerating under gravity with no other force acting on it.

Question 11

Define impulse.

Answer 11

The product of force and the time for which the
force acts.

Question 12

Define inelastic collision.

Answer 12

A collision in which kinetic energy is lost.

Question 13

Define instantaneous speed.

Answer 13

The speed at the moment it is measured — speed over an infinitesimal
interval of time.

Question 14

Define kinetic energy.

Answer 14

The energy associated with an object as a result of its motion.

Question 15

Define linear momentum.

Answer 15

The product of mass and
velocity of an object- a vector quantity.

Question 16

Define moment.

Answer 16

The product of force and perpendicular distance from a pivot or stated point.

Question 17

State Newton’s first law of motion.

Answer 17

A body will remain at rest or continue to move with constant
velocity unless acted upon by a resultant force.

Question 18

State Newton’s second law of motion.

Answer 18

The rate of change of momentum of an object is directly
proportional to the resultant force and takes place in the direction of the force.

Question 19

State Newton’s third law of motion.

Answer 19

When two objects interact, each exerts an equal but opposite
force on the other during the interaction.

Question 20

Define normal contact force.

Answer 20

The force exerted by a surface on an object, which acts perpendicularly to
the surface.

Question 21

Define power.

Answer 21

The rate of work done.

Question 22

Define pressure.

Answer 22

The force exerted per unit cross-sectional area.

Question 23

State the principle of conservation of energy.

Answer 23

The total energy of a closed system remains constant.

Question 24

State the principle of conservation of momentum.

Answer 24

Total momentum of a closed system remains the constant.

Question 25

State the principle of moments.

Answer 25

For a body in rotational equilibrium, the sum of the anticlockwise
moments about a point is equal to the sum of the clockwise moments about the same point.

Question 26

Define stopping distance.

Answer 26

The total distance travelled from the time when a driver first sees a reason to stop to the time when the vehicle stops, the sum of the thinking distance and the braking
distance.

Question 27

Define terminal velocity.

Answer 27

The constant speed reached by an object when the drag force (and upthrust) is equal and opposite to the weight of the object.

Question 28

Define thinking distance.

Answer 28

The distance travelled by a vehicle from when the driver first perceives a
need to stop to when the brakes are applied.

Question 29

Define torque (of a couple).

Specifically torque of a couple.

Answer 29

The product of one of the forces of a couple and the perpendicular distance between the forces.

Question 30

Define upthrust.

Answer 30

The upward buoyant force exerted on a body immersed in a fluid.

Question 31

Define velocity.

Answer 31

A vector quantity equal to the rate of change of displacement.

Question 32

Define weight.

Answer 32

The gravitational force on an object.

Question 33

Define work.

Answer 33

The product of force and the distance moved in the direction of the force.

(Transfer of energy)

Question 34

Define couple.

In the context of forces and moments.

Answer 34

A pair of equal and opposite forces acting on a body but not in the same straight line.

Question 35

Define the unit N.

Answer 35

1 Newton is the force that would accelerate a 1kg object at 1 m/s^2

Question 36

Define average velocity.

Answer 36

Displacement divided by change in time.

Question 37

Define average acceleration.

Answer 37

Change in velocity divided by change in time.

Question 38

What quantity is represented by the area under a velocity-time graph?

Answer 38

Displacement.

Question 39

What quantity is represented by the area under an acceleration-time graph?

Answer 39

Change in velocity.

Question 40

What quantity is represented by the area under a force-time graph?

Answer 40

Impulse.

Question 41

What quantity is represented by the area under a force-distance graph?

Answer 41

Work.

Question 42

Define tension.

Answer 42

The pulling force exerted by a string, cable, or chain on an object.

Question 43

Define density.

Answer 43

Mass per unit volume.

Question 44

Define gravitational potential energy.

Answer 44

The energy associated with an object as a result of its position in a gravitational field.

Question 45

Define efficiency.

Answer 45

The ratio of useful output energy to input energy.

Question 46

Define elastic collision.

Answer 46

A collision in which no kinetic energy is lost.

Question 47

Define the unit Joule.

Answer 47

1 Joule is the energy transferred when a force of 1 N is applied over a distance of 1 m.

Question 48

State Archimedes’ principle

Answer 48

The upthrust exerted on a body by the fluid that the body is immersed in (both fully and partially) is equal to the weight of fluid that the body displaces.

Question 49

Define fluid.

Answer 49

A substance that can flow.