1. Construct a glossary of the key terms in this unit. You could
add it to the one you made for Units 1 and 2. 2. Describe what happens to a ball when you drop it from a height
of 2 metres.
3. Explain the difference between average velocity and instantaneous velocity.
4. A bus travels 80 km due south in 2 hours. It then travels 100 km due west in 3 hours. What is the average velocity of the bus?
5. A car is travelling at 50km / h The driver sees a child run out into the road 5 m ahead. She applies the breaks and the car stops in 5 seconds. The driver's thinking time is 1.5 s.
a) Will the car stop in time?
b) If the driver's thinking time is increased to 2.5 s, will the car stop in time?
c) What happens if the thinking time is 1.5 s but the car is travelling at 64km / h
6. What assumption do you have to make if you are asked to do a
calculation on a falling body?
7. A boy walks to school. He walks 3 km in 30 minutes. He meets some friends and they talk for 10 minutes before they carry on walking to school. They walk 1 km in 15 minutes.
a) Draw a displacement-time graph to show the boy's journey to school.
b) What was the average velocity of the boy's journey? Give your answer in m / s
8. Explain, in terms of forces and acceleration, what happens
when a body is moving in uniform horizontal circular motion. 9. How do the forces on a body moving in a vertical circle vary?
10. What is the difference between radial and tangential acceleration?
11. What is relative velocity?
1. To construct a glossary of key terms in this unit, you can start by looking through the material or textbook provided for the unit. Identify words or phrases that are important and relate to the concepts being discussed. Write down each term and its definition or explanation. You can also include any relevant formulas or equations.
2. When a ball is dropped from a height of 2 meters, it falls towards the ground due to the force of gravity. As it falls, its potential energy is converted into kinetic energy. The ball accelerates towards the ground at a constant rate of 9.8 m/s² (assuming no air resistance). Upon reaching the ground, the ball bounces back up, with some of the kinetic energy being transferred back into potential energy. The ball continues to bounce until it eventually comes to a stop.
3. Average velocity and instantaneous velocity are both used to describe an object's motion but differ in terms of the time interval over which they are calculated. Average velocity is calculated by dividing the displacement of an object by the time it takes to cover that distance. It gives an overall measure of how fast and in what direction an object is moving. Instantaneous velocity, on the other hand, refers to the velocity of an object at a specific instant in time. It is determined by finding the slope of the displacement-time graph at that particular point.
4. To calculate the average velocity of the bus, you need to find the total displacement and the total time taken. Since the bus travels 80 km due south and 100 km due west, the total displacement is the vector sum of these displacements. Use the Pythagorean theorem to find the magnitude of the displacement. Then, divide the magnitude by the total time taken (2 hours + 3 hours) to find the average velocity.
5. a) To determine if the car will stop in time, calculate the distance it will travel during the thinking time by multiplying the initial velocity (50 km/h) by the thinking time (1.5 s). Then, calculate the distance it will take to stop by using the formula s = (v^2) / (2a), where v is the initial velocity and a is the deceleration. If the distance traveled during thinking time is less than or equal to the distance to stop, the car will stop in time.
b) Repeat the calculations in (a), but with the increased thinking time of 2.5 s. Compare the distance traveled during thinking time to the distance to stop. If the former is still less than or equal to the latter, the car will stop in time.
c) Calculate the stopping distance using the same formula as before, but with the higher initial velocity of 64 km/h. Compare this to the distance traveled during thinking time. If the latter is greater than the former, the car will not stop in time.
6. When calculating on a falling body, it is assumed that there is no air resistance acting on the body. This assumption helps simplify the calculations and gives a more idealized representation of the motion.
7. a) To draw a displacement-time graph for the boy's journey to school, plot the distance covered at each respective time interval. Start at the origin (0,0) and plot a point at (30 minutes, 3 km). Then, plot the second point at (40 minutes, 4 km). Connect the two points with a straight line.
b) To find average velocity, divide the total displacement (4 km) by the total time taken (40 minutes or 2400 seconds). Convert the answer to m/s by dividing the distance in meters by the time in seconds.
8. When a body is moving in uniform horizontal circular motion, it experiences a centripetal force directed towards the center of the circular path. This force is responsible for continuously changing the direction of the body's velocity without changing its speed. As a result, the body undergoes acceleration towards the center of the circle, which is known as centripetal acceleration.
9. The forces on a body moving in a vertical circle vary throughout the motion. At the top of the circle, there are two forces acting on the body: gravity pulling it downwards and the tension in the string (or any other force) pulling it upwards. The net force at this point provides the centripetal force required for circular motion. At the bottom of the circle, the net force is the difference between the gravitational force and the tension in the string, acting downwards. This difference provides the centripetal force.
10. Radial acceleration refers to the acceleration directed towards or away from the center of circular motion. It is perpendicular to the tangential direction and is given by the formula aᵣ = v²/r, where v is the speed and r is the radius of the circular path. Tangential acceleration, on the other hand, is the component of acceleration tangential to the circular path. It can be caused by changes in speed or changes in direction.
11. Relative velocity refers to the velocity of an object or observer relative to another. It is the difference between the velocities of two objects or the velocity of an object relative to a stationary reference frame. In simple terms, it measures how fast one object is moving with respect to another object or point of reference.