PHYCS 101 Test 1 Spring 2003

Physics Department 8/4/2003

Use: g = 10 m/s², sin 37^o = cos 53^o = 0.6, sin 53^o = cos 37^o = 0.8

Choose the correct answer for the following questions:

1. A particle moves along the x-axis with its coordinate given by x = t² – 2t + 3m where x in m and t in s. Find its velocity in m/s at t = 2s.

a) 2 b) 4 c) 6 d) 8

Solution:

2. A car starts accelerating uniformly from an initial velocity . After 10 seconds, the velocity increases to 30 m/s during which it travels a distance of 175 m. Find the car’s initial velocity in m/s.

a) 5 b) 10 c) 15 d) 20

Solution:

3. A ball is thrown vertically upward so that it reaches a maximum height

h_max = 25m from ground. What is its speed in m/s when it is at y = 20 m high?

_x

h_max

a) 10.0 b) 14.1 c) 17.3 d) 20.0 u

Solution: y

4. A particle initially at rest at the origin, starts to move in the xy-plane with a constant acceleration of . Find its position vector in m at t = 2 seconds.

a) b) c) d)

Solution:

5. A projectile is fired horizontally with a speed of from the top of a h = 30 m high building. How far from the base of the building (x) in m will the projectile hit the ground?

a) 98.0 b) 113.1 c) 126.5 d) 138.6

Solution:

h

6. In the figure, F₁=50 N and F₂=20 N. Find the magnitude of the net (resultant) force in N.

y

a) 53.9 b) 58.3 c) 64.0 d) 70.7

x

Solution: F₁

7. A 1000 kg car initially traveling at 20 m/s stops in a distance of 100 m. Find the magnitude of the net force in N acting to stop the car.

a) 2000 b) 2500 c) 4000 d) 5000

Solution:

8. A force F prevents a 2 kg brick from falling by pressing it against a vertical wall. If the coefficient of static friction between the brick and the wall , what minimum force F in N must be used?

F

a) 25 b) 40 c) 50 d) 100

mg

Solution:

9. For the system shown m₁ = 10 kg and m₂ = 8 kg and the coefficient between m₂ and the surface m_k = 0.5. Find the acceleration of m₁.

a

a) 1.1 b) 2.5 c) 4.3 d) 6.7

a

37^o

m₂

m_k

m

Solution:

10. A 1000 kg car traveling without skidding on a flat circular path of radius r = 80 m with a constant speed v = 20 m/s. What is the magnitude of the static frictional force f_s in N?

a) 5000 b) 8000 c) 10000 d) 20000

f_s

R

Solution: v