1.1 Impulse and Momentum

Question 1

Equation for linear momentum?

Answer 1

p = mv 
where 
p = momentum (kgms^-1) 
m = mass (kg) 
v = velocity (ms^-1)

Question 2

Is momentum a vector or a scalar?

Answer 2

a vector

Question 3

If there is no external forces acting on the system is momentum conserved?

Answer 3

Yes

Question 4

What is the impulse?

Answer 4

Force x time,

Question 5

What is impulse in terms of momentum?

Answer 5

The rate of change of momentum, we can see this from newton’s second law (Ft = mv)
REMEMBER it is the change in momentum and time

Question 6

Is impulse the same as force?

Answer 6

No it has units Ns while force has units N

Question 7

What is the area under a force time graph equal to?

Answer 7

The impulse

Question 8

What does impulse play a big part in?

Answer 8

Car safety and ball games

Question 9

What needs to happen in a head on collision to reduce the force felt by the system and hence the passengers of the vehicle?

Answer 9

Increase the collision time, which means the impulse would be greater.
Max force is smaller and time is greater

Question 10

How is this done in a car?

Answer 10

Crumple zones and air bags

Question 11

During shorter and longer collisions would the impulse still be the same?

Answer 11

Yes, even if time is changed (area under the graph stays the same)

Question 12

In football the longer the foot remains in contact with the ball the greater the what?

Answer 12

The impulse for a given kicking force. The ball will be able to travel with more speed! (due to greater momentum)

Question 13

How do shinpads make use of impulse?

Answer 13

Increase reaction time decreasing the force felt

Question 14

Why is string tension import in tennis?

Answer 14

Greater tension means more control of the ball due to smaller impulse, it costs the speed of the ball

Loosely tightened means less control due to increased impulse but greater speed of the ball (greater change in momentum )

Question 15

With what equipment can we investigate impulse?

Answer 15

Having an air track with a trolley containing masses, string connecting trolley to hanging masses through the use of a pulley. Also light gates at the beginning and end of the air track.

Question 16

How does this practical work?

Answer 16

We release the trolley at the end of the air track, it moves by the gravitational force exerted on the hanging masses due to the gravitational field. We find velocity at each light gate and calculate the change in momentum. (as long as the string is inextensible the change in velocity between trolley and hanging masses is equal). We can also find the change in time between 2 light gates and work out impulse by assuming the force is equal to the weight of the hanging masses. Either way we take repeats for varying hanging masses (removed to and from trolley). A graph of force against impulse should be a straight line.