# Isaac physics; heeelp!

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Thread starter 2 years ago
#1
When a car of mass 1000kg is travelling along a level road at a steady speed of 20ms−1, its engine is working at 18kW.

a. Find the magnitude and direction of the resistive force due to friction, which may be taken to be constant.

b. The engine is suddenly disconnected and the brakes applied, and the car comes to rest in 50m. Find the force, assumed constant, exerted by the brakes.

c. Find also the distance in which the car, travelling at 20ms−1, would come to rest if the engine were disconnected and the same braking force applied on an upward incline of angle θ, where sinθ=1/20.

d. By how much does this change if the car is travelling down the same hill at 20ms−1?

i have done all but part d, please help
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2 years ago
#2
Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.
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2 years ago
#3
While I am not a fan of the wording of part d, the question definitely requires you to find the distance the car from the time the brakes are applied if the car is going downhill rather than uphill.
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2 years ago
#4
(Original post by Almavaligarous)
When a car of mass 1000kg is travelling along a level road at a steady speed of 20ms−1, its engine is working at 18kW.

a. Find the magnitude and direction of the resistive force due to friction, which may be taken to be constant.

b. The engine is suddenly disconnected and the brakes applied, and the car comes to rest in 50m. Find the force, assumed constant, exerted by the brakes.

c. Find also the distance in which the car, travelling at 20ms−1, would come to rest if the engine were disconnected and the same braking force applied on an upward incline of angle θ, where sinθ=1/20.

d. By how much does this change if the car is travelling down the same hill at 20ms−1?

i have done all but part d, please help
What are you stuck with for (d)?

As the car moving down the hill, the component of the weight parallel to the slope is helping the car to accelerate down the slope, so the net force of slowing down the car is smaller than that of the (c).
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