**PreQuiz 7.1 - **Impulse and Momentum** .:.
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The Formulas:

p = momentum in kgm/s

v = velocity in m/s

m = mass in kg

Impulse = change in momentum (kgm/s)

F = Force in N

Dt = elapsed time in s

m = mass in kg

Dv = change in velocity

F = force in N

Dp = change in momentum (kgm/s)

Dt = elapsed time (s)

The Prequiz:

**1. A hammer has 12.4 kg m/s of momentum, and is going 8.5
m/s, what is its mass? (1.5 kg)**

Use

p = 12.4 kg m/s

v = 8.5 m/s

m = mass in kg - unknown

**2. A rocket exerts 10.3 N of force for 2.23 seconds.
What impulse does it impart? (23.0 Ns)**

use

F = 10.3 N

Dt = 2.23 s

Impulse = change in momentum (kgm/s) - unknown

3. A 17.5 N unbalanced force is exerted on a 67.1 Kg mass for 37.2 seconds. What is the change of velocity of the mass? (9.70 m/s)

use

F = 17.5 N

Dt = 37.2 s

m = 67.1 kg

Dv = change in velocity - unknown

**4. A .142 Kg baseball going 41 m/s, strikes a bat, and
heads straight back to the outfield at 53 m/s. If the bat exerted a
force of 2350 N, for what time was it in contact with the bat? (0.00568 s)**

use - but be careful - the difference between 41 m/s to the right and 53 m/s to the left is NOT 12 m/s.

F = -2350 N (toward the pitcher is negative)

Dt = elapsed time in s - unknown

m = 0.142 kg

Dv = -53 m/s - 41 m/s = -94 m/s

**5. A rocket engine burns fuel at a rate of 53.5 grams
per second, and develops a force of 65.2 N. What must be the exhaust
velocity? (1000 grams = 1 kg) (1220 m/s)**

use - use 1.0 s for Dt, convert grams to kg (divide by 1000)

F = 65.2 N

Dt = 1 second (it is per second)

m = 0.0535 kg

Dv = change in velocity - unknown