Forces and motion

Question 1

Define friction

Answer 1

A force that opposes something from moving over something else.It can change the direction or speed

Question 2

Define Gravity and state its acceleration

Answer 2

A force that attracts an object to another. Gravity is a constant of 10ms^-2

Question 3

Define acceleration and state its unit

Answer 3

Acceleration is the change in speed over time. It is measured in ms^-2

Question 4

State the acceleration equation

Answer 4

a=Δv/Δt

Question 5

What is the equation for speed and define speed

Answer 5

Speed is how fast an object travels. v=Δd/Δt

Question 6

How long does it take a bird to fly 12.5m at 2ms^-1?

Answer 6

v=Δd/Δt, 2=12.5/Δt, t=12.5/2, t=6.25 seconds

Question 7

What unit do we measure speed in?

Answer 7

ms^-1

Question 8

Define a force

Answer 8

A force is a push or a pull

Question 9

Define net force

Answer 9

The sum of all the forces acting on an object. When forces are in the same direction the forces are added together. Forces going in an opposite direction have their forces subtracted from one another.

Question 10

Balances forces are equal. They occur when the object is stationary or when the object _______________.

Answer 10

…is travelling at a constant speed.

Question 11

Balanced forces = ____

Answer 11

0N (in the test always state when forces = 0N)

Question 12

Unbalanced forces are _____(1). And will allow the object to _____(2).

Answer 12

(1)-unequal. (2)-accelerate/deccelerate.

Question 13

When driving it begins to rain. Road safety states you should double the expected stopping distance when driving in wet weather. Why is this? What force is decreased?

Answer 13

Friction is decreased. When the road is wet the tires have a harder time creating a greater amount of friction in a smaller period of time than they would on a normal day. This results in a greater amount of stopping time.

Question 14

A car is travelling at a constant speed. Is the thrust force equal or unequal to the drag?

Answer 14

They are equal. Since the object is travelling at a constant speed the forces are balanced resulting in a force of 0N.

Question 15

What is the equation for force and what unit is it measured in

Answer 15

F=MA, newtons

Question 16

A drone accelerates forwards without moving up or down. In terms of balanced and unbalanced forces, explain why the drone is changing its motion side to side by accelerating forwards but not changing its motion up or down.

Answer 16

To accelerate, an object must have an unbalanced force. For the drone the thrust force is unequal with the drag force allowing it to accelerate. It stays at the same height because the support and gravity forces are balanced and equal to each other. Unbalanced forces change speed and balanced ones do not.

Question 17

Timothy accelerates a 400g ball at 12.3ms^-2. Calculate the force that Timothy must exert on the ball to cause this acceleration.

Answer 17

f=ma, f=0.4(400g = 0.4kg)*12.3, f=4.92N

Question 18

What is the difference between mass and weight?

Answer 18

Mass is the measure of the amount of matter in an object. Weight is the measure of the force on an object and is caused by the effect of gravity on that object.

Question 19

You drop a piece of paper and a scrunched up piece of paper. Will they accelerate at the same rate?

Answer 19

Yes they will. They accelerate at the same rate due to gravity. The flat pice of paper may take longer to reach the ground but that is because of surface area not acceleration.

Question 20

A car is travelling at 27ms^-2 then accelerates to 32ms^-1 in 2.5 seconds. Calculate the cars acceleration.

Answer 20

a=Δv/Δt, a=(32-27)/2.5, a=5/2.5, a=2ms^-2