I am a postgraduate student at the University of Bristol. **I have a constant curiosity to understand how things work**, which is why in school I most enjoyed physics. I then did an undergraduate degree in civil engineering, before focusing on water engineering.

During the tutorials, you will decide which topics to work on. I will help you by explaining concepts from different perspectives until you understand them well, and can explain them to me (and are tempted to explain them to your dad, and your sister, and the cab driver also!). **The best way to make things memorable is to make them enjoyable!** So I will make sure to keep things interesting by giving you **real world examples **where possible.

Engineers are all about coming up with **creative solutions, **and for that we need to use all the different resources we have. Once you have a basic understand, you will find that you can play around with the concepts you have learned and use them to** confidently approach any problem that comes at you. **

I am a postgraduate student at the University of Bristol. **I have a constant curiosity to understand how things work**, which is why in school I most enjoyed physics. I then did an undergraduate degree in civil engineering, before focusing on water engineering.

During the tutorials, you will decide which topics to work on. I will help you by explaining concepts from different perspectives until you understand them well, and can explain them to me (and are tempted to explain them to your dad, and your sister, and the cab driver also!). **The best way to make things memorable is to make them enjoyable!** So I will make sure to keep things interesting by giving you **real world examples **where possible.

Engineers are all about coming up with **creative solutions, **and for that we need to use all the different resources we have. Once you have a basic understand, you will find that you can play around with the concepts you have learned and use them to** confidently approach any problem that comes at you. **

Standard DBS Check

21/10/2014**a) Calculate the magnitude of the total momentum of the trucks. **

The momentum (p) is the mass (m) of an object multiplied by its velocity (v).

p = m x v

Velocity is different to speed, because it has a direction. Fortunately, the trucks in the question are travelling in exactly opposite directions, so we can express their velocities, one compared to the other, as one being negative, and the other one being positive. Lets decide to make "travelling due east" positive, and "travelling due west" negative.

momentum of truck A = mass of truck A x velocity of truck A

p1 = m1 x v1 = 1.2 kg x - 0.90 m/s = - 1.08 kg.m/s

momentum of truck B = mass of truck B x velocity of truck B

p2 = m2 x v2 = 4.0 kg x 0.35 m/s = 1.4 kg.m/s

total momentum of the trucks = momentum of truck A + momentum of truck B

p(total) = p1 + p2 = - 1.08 kg.m/s + 1.4 kg.m/s = 0.32 kg.m/s

The total momentum is positive, which means that it is in the east direction, or in the direction of truck B.

If we look back at the numbers, we see that the mass of truck B is 3.3 times bigger than mass of truck A (4.0 / 1.2 = 3.3), while the speed of truck B is only 2.6 times smaller than the speed of truck A (9.0 / 0.35 = 2.6), so it makes sense that truck B has greater momentum.

**b) The trucks collide and stick together. Determine their velocity after the collision. **

The trucks stick together after collision. When this happens we can assume that they become one big truck. The mass of the new truck will be:

mass of big truck = mass of truck A + mass of truck B

m3 = m1 + m2 = 1.2 kg + 4.0 kg = 5.2 kg

We also assume that the trucks are in a closed system, meaning that the total momentum before the collision is the same as the total momentum after the collision. We can write this as:

p1 + p2 = p3

or

m1v1 + m2v2 = m3v3

The question asks us to determine the velocity after the collision. We can therefore rearrange the equation above to solve for v3.

v3 = (m1v1 + m2v2) / m3 = 0.32 kg.m/s / 5.2 kg = 0.06 m/s

After the collision, the two trucks will be travelling together due east at a speed of 0.06 m/s.

**a) Calculate the magnitude of the total momentum of the trucks. **

The momentum (p) is the mass (m) of an object multiplied by its velocity (v).

p = m x v

Velocity is different to speed, because it has a direction. Fortunately, the trucks in the question are travelling in exactly opposite directions, so we can express their velocities, one compared to the other, as one being negative, and the other one being positive. Lets decide to make "travelling due east" positive, and "travelling due west" negative.

momentum of truck A = mass of truck A x velocity of truck A

p1 = m1 x v1 = 1.2 kg x - 0.90 m/s = - 1.08 kg.m/s

momentum of truck B = mass of truck B x velocity of truck B

p2 = m2 x v2 = 4.0 kg x 0.35 m/s = 1.4 kg.m/s

total momentum of the trucks = momentum of truck A + momentum of truck B

p(total) = p1 + p2 = - 1.08 kg.m/s + 1.4 kg.m/s = 0.32 kg.m/s

The total momentum is positive, which means that it is in the east direction, or in the direction of truck B.

If we look back at the numbers, we see that the mass of truck B is 3.3 times bigger than mass of truck A (4.0 / 1.2 = 3.3), while the speed of truck B is only 2.6 times smaller than the speed of truck A (9.0 / 0.35 = 2.6), so it makes sense that truck B has greater momentum.

**b) The trucks collide and stick together. Determine their velocity after the collision. **

The trucks stick together after collision. When this happens we can assume that they become one big truck. The mass of the new truck will be:

mass of big truck = mass of truck A + mass of truck B

m3 = m1 + m2 = 1.2 kg + 4.0 kg = 5.2 kg

We also assume that the trucks are in a closed system, meaning that the total momentum before the collision is the same as the total momentum after the collision. We can write this as:

p1 + p2 = p3

or

m1v1 + m2v2 = m3v3

The question asks us to determine the velocity after the collision. We can therefore rearrange the equation above to solve for v3.

v3 = (m1v1 + m2v2) / m3 = 0.32 kg.m/s / 5.2 kg = 0.06 m/s

After the collision, the two trucks will be travelling together due east at a speed of 0.06 m/s.

Acceleration is a change in *velocity *over time. Velocity is different to speed, because it has a direction (for example a car moving at 10 mph along a road heading north will have a greater velocity due north than a car moving at 10 mph along a road heading north-east).

A particle moving in a circular path is constantly slightly changing its direction. Therefore its velocity is changing, and as a result so is its acceleration. If we take the particle to be a satellite and the circular path to be the orbit around the earth, the satellite is constantly accelerating towards the centre of the earth, like an object in free fall. However its forward velocity balances out the downward acceleration, which causes it to move in a circular path around the earth. The downward acceleration brings it lower only as much as the curvature of the earth itself.

Acceleration is a change in *velocity *over time. Velocity is different to speed, because it has a direction (for example a car moving at 10 mph along a road heading north will have a greater velocity due north than a car moving at 10 mph along a road heading north-east).

A particle moving in a circular path is constantly slightly changing its direction. Therefore its velocity is changing, and as a result so is its acceleration. If we take the particle to be a satellite and the circular path to be the orbit around the earth, the satellite is constantly accelerating towards the centre of the earth, like an object in free fall. However its forward velocity balances out the downward acceleration, which causes it to move in a circular path around the earth. The downward acceleration brings it lower only as much as the curvature of the earth itself.