## Phrases Used in Suvat Questions

SUVAT questions involve using the five equations To answer a SUVAT question you need three of the quantities s, u, v, a or t. Often however the values of some of these quantities is hidden behind phrases used in the question. Typical phrases and their meaning are shown in the table below. Phrase in Question […]

## Does it Really Matter Which Point You Take Moments About?

Not when the system is in equilibrium. When a system is in equilibrium, the sum of the moments about any point is zero. It is intuitive to take moments about some point the system might turn about, and this is often convenient and makes forces easier to find, since the forces acting at the point […]

## Advanced Projectile Questions

Advanced questions involving projectiles typically involve both horizontal and vertical components of motion. We use the equations of motion vertically and horizontally to find missing values ofandIn general values ofandare different considered horizontally and vertically, but the timeis the same at any instant of vertical or horizontal motion. In addition The horizontal component of acceleration […]

## Finding the Velocity Vector Given Speed and Direction

We can be given a velocity in more than one way. One way is to be given a speed together with a bearing. The velocity can be found using trigonometry. Example: A car is travelling at 50m/s on a bearing of 240 degrees. Find the velocity. The vertical componenent of the velocity is The horizontal […]

## Displacement, Velocity and Acceleration as Vectors

The displacement, velocity and acceleration of a particle have the same relationship in vector form as when motion is along a straight line: Integration and differentiation are done in a natural way, with the direction vectorsand being constant vectors. Example: The position vector,of a particle at timeis given by Find expressions for the acceleration and […]

## Force and Rate of Change of Momentum

Momentum is defined as mass* velocity: p=mv If we differentiate this expression for the momentum, assuming the mass is constant then Newton’s Second Law of Motion states that F=ma, so from this this we conclude which means that the rate of change of momentum equals Force. Using F=ma we can integrate with respect to time […]

## Hanging Particle Connected By a String to a Pulley on a Slope

If two particles P and Q are connected as in the diagram below… …the first thing to do is to draw all the forces acting on each particle. Note: The reactionis perpendicular to the surface. The Force of gravity always acts down The tension in the rope always acts towards the centre of the string. […]

## Cars and Trailers – Summary

When a car is pulling a trailer, we can applywhereis the resultant of all the forces on both car and trailer,is the mass of the car plus the mass of the trailer, and a is the acceleration, which, since the cable between the cable and car is always assumed inextensible, is the same for both […]

## SUVAT with Vectors

We don’t have to use the SUVAT equations only with motion in a straight line. In general the displacement, initial velocity, final velocity and acceleration are all vectors and we can write the SUVAT equations as vector equations. (1) (2) (3) (4) Ifandare along the same line then (4) can be written We can use […]