Motion

Question 1

State the 5 suvat equations

Answer 1

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

Question 2

What are the properties of mass?

Answer 2

• mass is a measure of inertia
• it depends on the amount of matter a body contains
• it does not change from place to place
• it is a scalar

Question 3

What are the properties of weight?

Answer 3

• Weight is a force
• it depends on the strength of gravity
• it can change from place to place
• it is a vector

Question 4

Describe and explain free fall (terminal velocity)

Answer 4

1. The body accelerates freely since the only force acting is weight
2. As velocity increases so does air resistance, the resultant force decreases and so acceleration decreases
3. When air resistance is equal and opposite to the weight of the body, the resultant force is zero, there is no acceleration and the body falls at terminal velocity

Question 5

What is a vector?

Answer 5

A vector is a physical quantity that has both magnitude and direction

Question 6

Give five examples of vector quantities

Answer 6

Displacement, velocity, force, acceleration and momentum

Question 7

What is a scalar?

Answer 7

A scalar is a physical quantity that has magnitude only

Question 8

Give five examples of scalar quantities

Answer 8

Answers include distance, speed, energy, power, pressure, temperature and mass

Question 9

How do vector diagrams work?

Answer 9

In a vector diagram a vector can be represented using a line. The length of the line represents the magnitude of the vector, and the direction of the line represents the direction of the vector.

Question 10

State the four ways you can work out the resultant vector of two or more vectors

Answer 10

• Scale drawing
• Pythagoras
• Sine and Cosine rules
• Resolving vectors

Question 11

Explain the process of calculating the resultant vector using scale drawing

Answer 11

To find the resultant vector of a + b we draw vector a then draw vector b from the end of a. The resultant is the line that connects the start and finish points, which can be measured.

Question 12

Explain the process of calculating the resultant vector using Pythagoras

Answer 12

If two vectors, x and y, are perpendicular to each other then the resultant can be found using the equation
z = √(x² + y²)

Question 13

Explain the process of calculating the resultant vector using Sine and Cosine rules

Answer 13

If three vectors form a closed triangle, then the sine and cosine rules can be used to relate the angles and lengths

Sine rule - sinA/a = sinB/b = sinC/c

Cosine rule - a² = b² + c² - 2bccosA

Question 14

How can a vector be resolved?

Answer 14

If we know the magnitude and direction of a vector (R) then we can calculate its vertical and horizontal components.
If the angle is between the vector and the horizontal then
Horizontal component = Rcosθ
Vertical component = Rsinθ

Question 15

What is the gradient of a displacement/time graph equal to?

Answer 15

Velocity

Question 16

What is the area under a velocity/time graph equal to?

Answer 16

Displacement

Question 17

What is the gradient of a velocity/time graph equal to?

Answer 17

Acceleration

Question 18

If two identical balls were released at the same time, one falling straight to the ground and one projected with a horizontal velocity, explain what would happen

Answer 18

The horizontal and vertical components of motion are independent of each other, so the balls would fall to the ground at the same rate. No matter how high the horizontal component of velocity, the projected ball would still take the same amount of time to reach the ground.

Question 19

State the characteristics of projectile motion for an object with initial velocity u

Answer 19

• an object with projectile motion follows a parabolic path
• the horizontal component of the velocity = ucosθ, and remains constant
• the initial vertical velocity = usinθ
• at the maximum height of the parabolic curve, the vertical component of velocity = 0