Motion and Forces Revision Cards

Question 1

What is a vector quantity?

Answer 1

A vector quanitity is a quantity that has both DIRECTION and MAGNITUDE

Question 2

What is the difference between mass and weight?

Answer 2

Mass is a scalar quantity, measured in kg and is the amount of matter in an object. Weight is a vector quantity, measured in N and is the force due to gravity on an object with mass.

Question 3

Define displacement

Answer 3

Displacement is the distance travelled in a straight line, in a given direction.

Question 4

Define velocity

Answer 4

Velocity is the speed in a particular direction.

Question 5

What is the equation that links speed, distance and time?

Answer 5

Speed (m/s) = distance (m) / time (s)

Question 6

What does the gradient of a distance time graph tell you?

Answer 6

Speed

Question 7

What does the gradient of a displacement time graph tell you?

Answer 7

Velocity

Question 8

What does a horizontal line on a displacement time graph tell you about the motion?

Answer 8

It is stationary

Question 9

What do the letters stand for in the equation a=(v-u)/t?

Answer 9

a = acceleration in m/s2
v = final velocity in m/s
u = initial velocity in m/s
t = time in s

Question 10

What is the acceleration due to gravity on Earth (g)?

Answer 10

g = 9.8m/s2
(This is often rounded to 10 in calculations)

Question 11

What does the gradient of a velocity time graph tell you?

Answer 11

Acceleration

Question 12

How do you calculate distance travelled from a velocity time graph?

Answer 12

Find the area under the line (you may need to break it into rectangles & triangles and add them together to find the total)

Question 13

A car is driving around a roundabout at 20km/h. It is said to be accelerating - why?

Answer 13

Speed isn’t changing, but velocity is changing because DIRECTION is changing. A Change in velocity is an acceleration.

Question 14

Which of Newton’s laws is this? “A moving object will continue to move at the same speed and direction unless an external force acts on it. A stationary object will remain at rest unless an external force acts on it.”

Answer 14

Newton’s FIRST law.

Question 15

What is a centripetal force?

Answer 15

A ‘centre-seeking’ force. A force that acts towards the centre of a circle. There is always a centripetal force if something is moving in a circle.

Question 16

What is the equation that links weight, mass and gravitational field strength? (Don’t forget units!)

Answer 16

Weight (N) = mass (kg) x gravitational field strength (N/kg)

Question 17

Why does a sky diver accelerate when he first jumps out of the plane?

Answer 17

There is a resultant force acting downwards, as his weight is much larger than the air resistance while he is moving slowly.

Question 18

Why does a sky diver stop accelerating some time after he jumps out of the plane?

Answer 18

As he speeds up air resistance increases. Eventually it gets so big in balances his weight. There is no resultant force, so no acceleration.

Question 19

What is the equation usually linked with Newton’s second law?

Answer 19

F = m a
where
F = resultant force (N)
m = mass (kg)
a = acceleration in the direction of the force (m/s2)

Question 20

Define inertial mass

Answer 20

Force(N) / Acceleration (m/s2)
How difficult it is to change the velocity of an object

Question 21

Which of Newton’s laws is this? “If object A exerts a force on object B, object B exerts an equal but opposite force on object A”.

Answer 21

Newton’s THIRD law.

Question 22

Action - reaction pairs act on _ _ _ _ _ _ _ _ _ objects.

Answer 22

Different

Question 23

What is the equation for momentum? (Don’t forget units!)

Answer 23

Momentum (kg m/s) = mass (kg) x velocity (m/s)

p = m v

Question 24

What is the equation that relates rate of change of momentum with force?

Answer 24

F = (mv - mu)/t

Question 25

How can you reduce the force felt in a collision?

Answer 25

Increase the time taken to reduce the momentum to zero.
(F = (mv - mu)/t)

Question 26

What is conservation of momentum?

Answer 26

The total momentum before a collision/explosion = the total momentum after the collision/explosion

Question 27

What is the equation for stopping distance?

Answer 27

Stopping distance (m) = thinking distance (m) + braking distance (m)

Question 28

What factors affect thinking distance?

Answer 28

those that affect reaction time, e.g. use of drugs/alcohol/caffeine, tiredness, distractions
AND
the speed of the car

Question 29

What factors affect braking distance?

Answer 29

those that affect the car itself, e.g. quality of the tyres/road surface/brakes, the weather conditions
AND
the speed of the car

Question 30

What is the purpose of a crumple zone?

Answer 30

To extend the TIME taken to bring the car to a halt, thus reducing the force felt by the passengers.
F = (mv - mu)/t

Question 31

Other than a crumple zone, which safety feature of a car works by increasing the time taken for the driver of a car to come to a stop?

Answer 31

Air bag