3 questions about Impulse equation

1. A car with a mass of 250 kg is moving with a speed of 72 km/hour, then accelerated with a constant force so that in 5 seconds its speed becomes 80 km/hour. Determine the impulse for 5 seconds

__Known:__

The mass of the car (m) = 250 kg

Initial speed (v_{o}) = 72 km/h = 20 m/s

Final speed (v_{t}) = 80 km/h = 22 m/s

Time interval (t) = 5 seconds

__Wanted:__ Determine impulse (I)

__Solution:__

Impulse formula: Impulse = Change in momentum

I = Δp

I = m (v_{t} – v_{o}) = (250)(22 – 20) = (250)(2)

I = 500 kg m/s

2. An object with a mass of 0.4 kg initially moving with a speed of 20 m/s is stopped by a constant force of 50 N in a certain time. How big is the impulse?

__Known____:__

Mass (m) = 0.4 kg

Velocity (v_{o}) = 20 m/s

Final velocity (v_{t}) = 0 m/s

Force (F) = 50 N

__Wanted:__ Impulse (I)

__Solution:__

Impulse formula: Impulse = Change in momentum

I = Δp

I = m (v_{t} – v_{o}) = (0,4)(0 – 20) = (0,4)(-20)

I = 8 kg m/s

3. An object with mass m is moving at a constant speed v, so the impulse of the object is…

Solution

Impulse = change in momentum. Momentum changes when mass or velocity changes. So if the speed and mass are constant then there is no change in momentum. So that there are no impulses.