Multiple Choice (1 point each) For questions 1-5 consider a car driving along a
ID: 1882899 • Letter: M
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Multiple Choice (1 point each) For questions 1-5 consider a car driving along a straight stretch of road after a snowstorm. Assume that we can ignore friction because the snow makes the road really slick, which means that the car can't brake or accelerate. We define the horizontal direction in which the cear is facing as the + direction and up as the +i direction, with [1.0 and-jo, 1. 1. The first part of the road is level. At some moment the car is traveling forward at 10 m/s the net force on the car is (a) Positive (b) Zero (c) Negative (d) We need more information to tell a magnitude of 5 m/s2. Which of these could be the car's acceleration vector? (b) [3,-4 m/s? 2. The next part of the rond goes down a hill. This results in the car accelerating downhill with (c) [5, -5) m/s (d) [-5,5] m/s (e) None of these conld be the car's acceleration vector 3. After making it down the first hill, the car then goes up another very long hill with a constant slope. If the car's acceleration is 2 m/s2 backward and it has an initial velocity of 20 m/s in the forward direction at the bottom of the hill, how long before the car comes to a stop? (a) 5s (b) 10 s (c) 20s (d) 40 s (e) None of these are correct 4. In the last problem how far did the car travel up the hil? (a) 20 m (b) 30 m (c) 200 m (d) 300 m (e) None of these are correctExplanation / Answer
1) b) zero
As the car is moving with constant veolcity net force must be zero.
2) b) [3,-4] m/s^2
becaue, a = sqrt(3^2 + 4^2)
= 5 m/s^2
ax = 3 m/s^2
ay = -4 m/s^2
negative sign indicates -y direction.
3) b) 10 s
using, v = u + a*t
==> t = (v - u)/a
= (0 - 20)/(-2)
= 10 s
4) e) None of theese are correct.
d = u*t + (1/2)*a*t^2
= 20*10 + (1/2)*(-2)*10^2
= 100 m
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