Mechanics

Question 1

Define velocity

Answer 1

The rate of change of displacement. v = s/t

Question 2

Define acceleration

Answer 2

The rate of change of velocity. a = (v-u)/t

Question 3

What is a moment

Answer 3

The turning effect of a force. Moment = force x perpendicular distance from the pivot to the force.

Question 4

Define the principle of moments

Answer 4

For an object to be in rotational equilibrium, the sum of the anticlockwise moments is equal to the sum of the clockwise moments about the same point.

Question 5

Define the centre of gravity

Answer 5

The point at which all weight of a body appears to act

Question 6

Define Newton’s First Law

Answer 6

An object will remain at rest or at constant velocity unless a resultant force acts upon it.

Question 7

Define Newton’s Second Law

Answer 7

Force = mass x acceleration. If the acceleration is 0ms^’2 then Force is 0N.

Question 8

Define Newton’s Third Law

Answer 8

Every action has an equal and opposite reaction. Forces always come in pairs.

Question 9

Define momentum

Answer 9

Momentum is a measure of an objects motion. Momentum = mass x velocity. p=mv. kgms^-2

Question 10

What are the SUVAT equations?

Answer 10

v^2 = u^2 + 2as
s = ut +1/2at^2
v = u + at
s = 1/2(u+v)t

Question 11

Define projectile

Answer 11

The motion of anything launched into the air and the forces acting on it are air resistance and gravity.

Question 12

How would you determine the horizontal and vertical velocities?

Answer 12

Vertical: Acceleration is constant, therefore SUVAT
Horizontal: No horizontal force (acceleration), therefore v = s/t

Question 13

Define an elastic collision

Answer 13

Kinetic energy is conserved.

Question 14

Define an inelastic collision

Answer 14

KE is not conserved. Lost energy will have been transferred to heat and sound energy.

Question 15

Derive an equation for particle momentum

Answer 15

E=1/2mv^2 p=vm
E=1/2m(p/m)^2
E=p^2/2m

Question 16

Define impulse and state the equation.

Answer 16

The change in momentum.

Impulse (Ns) = Force(N) x time (s)

Question 17

Define angular velocity

Answer 17

The rate at which angular displacement changes. Unit - radians per second.

Question 18

Define angular displacement

Answer 18

the vector measurement of the angle through which something has moved.

Question 19

Angular Velocity equations

Answer 19

ω=θ/T
v = ωr
T = 2π/ω

Question 20

Define centripetal acceleration

Answer 20

the acceleration towards the centre of a circle corresponds to the changes in direction to maintain motion around circle

Question 21

Centripetal acceleration

Answer 21

a= rω^2

Question 22

Define centripetal force

Answer 22

The resultant force towards the centre of the circle to maintain an objects circular motion

Question 23

centripetal force

Answer 23

F = mrω^2 =mv^2/r

Question 24

Centripetal force needed will be larger if:

Answer 24

• rotating object has more mass.
• objects rotate faster.
• object is further away from the centre of circle.

Question 25

Explain why a body moving at constant speed in a circular path needs a resultant force
acting on it.

Answer 25

The direction of speed/velocity is changing. There is an acceleration/rate of change in momentum

Question 26

Define power

Answer 26

Rate of energy transfer. P=E/t

Question 27

Equation for work done

Answer 27

W=Fd

Question 28

A projectile would have a greater range on the Moon than the Earth because of the
lower gravitational field strength and because of the lack of an atmosphere. Explain how each of these factors would increase the range of the projectile.

Answer 28

Smaller acceleration, causing longer time of flight. No work done against friction, as there is a lack of atmosphere.

Question 29

Explain why pulling the trolley a certain distance requires the person to do less work than pushing the trolley the same distance

Answer 29

Pulling trolley gives upwards force on the trolley, so there is less normal contact force. Friction is less. Less force is required to from the person. W=Fd, so less work done.