Chapter 5A: Forces

Question 1

How do you calculate the speed on a distance time graph?

Answer 1

The gradient of the line

Question 2

What is the formula for acceleration?

Answer 2

Change in velocity (m/s) / Time taken (s)

Question 3

How do you calculate the distance traveled on a velocity time graph?

Answer 3

The area under the graph

Question 4

How do you calculate the acceleration on a velocity time graph?

Answer 4

The gradient of the line

Question 5

What is the SUVAT equation?

Answer 5

final velocity^2 (m/s) - starting velocity^2 (m/s) = 2 * acceleration (m/s) * distance (m)

Question 6

Why do feathers fall slowly?

Answer 6

The air resistance on them is close to their weight

Question 7

What does the air resistance depend on?

Answer 7

The area and the speed

Question 8

Why do objects reach terminal velocity?

Answer 8

Their weight is balanced by the air resistance

Question 9

What is Newton’s 1st law?

Answer 9

When the resultant force acting on an object is 0, the object will not accelerate

Question 10

What is Newton’s 2nd law?

Answer 10

When there are unbalanced forces acting on an object, it will accelerate

Question 11

What is the equation that links mass to acceleration and force?

Answer 11

Force (N) = Mass (kg) x Acceleration (m/s^2)

Question 12

What is inertia?

Answer 12

A measure of how difficult it is to change an object’s motion (inertial mass = force * acceleration)

Question 13

What is Newton’s 3rd law?

Answer 13

Every force has a paired equal and opposite force?

Question 14

What is momentum?

Answer 14

The product of mass and velocity. It’s a vector

Question 15

What is the equation for momentum?

Answer 15

momentum (kgm/s) = mass (kg) * velocity (m/s)

Question 16

What is the equation that links mass to force and acceleration?

Answer 16

force = (change in momentum) / time

Question 17

Why do cars have crumple zones?

Answer 17

So that by buckling, they increase the impact time, decreasing the force

Question 18

Why do cars have seatbelts?

Answer 18

Because in the time it takes for the crumple zone to buckle, you’ll fly forwards into something

Question 19

What is the law of conservation of momentum?

Answer 19

When two objects collide, they have the same momentum as before the collision

Question 20

What is a closed system?

Answer 20

A system with no external forces acting on it

Question 21

How do you calculate the new speed of two objects after they collide?

Answer 21

New speed = (combined momentum) / (combined weight). Remember that since momentum is a vector, things moving relatively backwards have negative momentum

Question 22

What is the formula for kinetic energy?

Answer 22

(mv^2)/2

Question 23

What is the formula for work done?

Answer 23

Work done (J) = Force (N) * Distance (m)

Question 24

Describe a parachutist’s descent

Answer 24

After jumping, he accelerates at 9.8m/s^2, but the effects of air resistance eventually slow his acceleration until he reaches terminal velocity (the air resistance is the same as his weight). After opening his parachute, the increased surface area causes increased air resistance, meaning he continues falling at a lower terminal velocity