# Pushing a stalled car out of an intersection

• carodog
Otherwise, it is the change in momentum of the object. In summary, to find the final velocity of a car after being pushed for time t, use the relationship between impulse and momentum. By setting the initial momentum to 0 and solving for the final momentum, we can find the final velocity to be 11.48 m/s. To determine the displacement, use a kinematic equation and set the initial velocity to 0, then solve for acceleration and use a distance-time relation to find the displacement.
carodog
Homework Statement
A student is attempting to push his stalled car out of an intersection with his girlfriend at the wheel. The car and girlfriend has a combined mass of m = 965 kg. Unfortunately the hill has an incline of θ = 2.2 degrees with respect to the horizontal. The student can supply a force of F = 852 N for t = 13 s before tiring. What is the furthest the edge of the intersection can be (d) in meters from the stalled car in order to make it out in one push? Assume no rolling resistance from the car and that his girlfriend brakes to bring the car to a stop when he stops pushing.
Relevant Equations
m = 965 kg
θ = 2.2 degrees
F = 852 N
t = 13 s
Hints given:
-Start with free body diagram. Use the relationship between impulse and momentum to find the final velocity of the car after he has pushed for time t.
-Use a kinematic equation to relate the final velocity and time to the distance traveled.
-What is his initial velocity?

My attempt:
Impulse = F (delta t) = change in momentum = 852N (13s) = 11076 Ns

Initial momentum = 0 Ns
Final momentum = 11076 Ns = mv = (965kg) v
Final velocity v = 11.48 m/s

Not sure where to go from here. Thinking maybe I should be splitting things up into x- and y- components and then using the v-t relation: delta v = a (delta t). If initial velocity is 0 (braking) then I could solve for acceleration and then use x-t relation: (delta x) = (initial v)(delta t) + (.5a(delta t)^2) to find displacement...

carodog said:
Impulse = F (delta t) = change in momentum
Only if that is the net force.

## 1. How do you safely push a stalled car out of an intersection?

First, make sure to turn on your hazard lights and use safety triangles or flares to alert other drivers. Then, gather a group of people to help push the car. Make sure everyone is positioned safely and in a line behind the car, facing the direction you want to push it. Once everyone is ready, begin pushing in a synchronized manner.

## 2. Is it okay to push a car by yourself?

No, it is not recommended to push a stalled car by yourself. It can be dangerous and difficult to control the car's direction and speed without assistance. It is best to gather a group of people to help push the car.

## 3. What is the best way to push a car uphill?

If possible, try to find a different route that does not involve pushing the car uphill. If it is unavoidable, make sure to have a larger group of people to help push and take breaks as needed. You may also need to use the car's brakes to control its speed while pushing.

## 4. Can pushing a car out of an intersection cause damage?

In most cases, pushing a car out of an intersection should not cause any damage. However, if the car has a manual transmission, pushing it in gear can cause damage to the transmission. It is best to push the car in neutral or with the engine off to avoid any potential damage.

## 5. What should I do if the car won't budge?

If the car won't move, do not force it. This can cause damage to the car or injury to yourself and others. Instead, try to find a tow truck or other professional assistance to safely move the car out of the intersection.

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