1017-311-6 (Dr. O’Dea) University Physics IExam #1

Name: ______

Exam Score: ______

READ the following instructions:

  1. The exam is closed book and closed notes.
  1. Calculators and the equations provided below are allowed.
  1. For numerical problems: Show all of your work.
  1. Problems 1-15 are worth 6 pts each and problem 16 is worth 10 pts.

Generally, you should show a minimum of four steps.

Diagram, if appropriate.

What general equation are you "plugging into"?

What are your substitutions? Be certain to include UNITS with numbers.

What is your final answer? Place a box around your final answer.

Near earth g = 9.8 m/s2

1..Let and . The vector sum is:

A.

B.

C.

D.

E.none of these

2.In the diagram, has magnitude 12m and has magnitude 8m. The x component of is about:

A.5.5m

B.7.6m

C.12m

D.14m

E.15m

3.A particle goes from x= –2m, y=3m, z=1m to x=3m, y=–1m, z=4m. Its displacement is:

A.

B.

C.

D.

E.

4.Two bodies are falling with negligible air resistance, side by side, above a horizontal plane. If one of the bodies is given an additional horizontal acceleration during its descent, it:

A.strikes the plane at the same time as the other body

B.strikes the plane earlier than the other body

C.has the vertical component of its velocity altered

D.has the vertical component of its acceleration altered

E.follows a straight line path along the resultant acceleration vector

Ans: A

5.The airplane shown is in level flight at an altitude of 0.50 km and a speed of 150 km/h. At what distance d should it release a heavy package to hit the target X? Take the magnitude of the local gravitational strength to be 10N/kg2.

A.150m

B.295m

C.420m

D.2550m

E.15,000m

6.Which of the curves on the graph below best represents the vertical component vy of the velocity versus the time t for a projectile fired at an angle of 45 above the horizontal?

A.OC

B.DE

C.AB

D.AE

E.AF

  1. A dart is thrown horizontally toward X at 20m/s as shown. It hits Y 0.1s later. The distance XY is:

A.2m

B.1m

C.0.5m

D.0.1m

E.0.05m

8. A toy racing car moves with constant speed around the circle shown below. When it is at point A its coordinates are x=0, y=3m and its velocity is . When it is at point B its velocity and acceleration are:

A. and , respectively

B. and , respectively

C. and , respectively

D. and , respectively

E. and 0, respectively

9. The iron ball shown is being swung in a vertical circle at the end of a 0.7-m long string. How slowly can the ball go through its top position without having the string go slack?

A.1.3m/s

B.2.6m/s

C.3.9m/s

D.6.9m/s

E.9.8m/s

10. A 5-kg block is suspended by a rope from the ceiling of an elevator as the elevator accelerates downward at 3.0m/s2. The tension force of the rope on the block is:

A.15N, up

B.34N, up

C.34N, down

D.64N, up

E.64N, down

11.A crate with a weight of 50N rests on a horizontal surface. A person pulls horizontally on it with a force of 10N and it does not move. To start it moving, a second person pulls vertically upward on the crate. If the coefficient of static friction is 0.4, what is the smallest vertical force for which the crate moves?

A.4N

B.10N

C.14N

D.25N

E.35N

12. A car is traveling at 15m/s on a horizontal road. The brakes are applied and the car skids to a stop in 4.0s. The coefficient of kinetic friction between the tires and roadis:

A.0.38

B.0.69

C.0.76

D.0.92

E.1.11

13. Block A, with a mass of 50kg, rests on a horizontal table top. The coefficient of static friction is 0.40. A horizontal string is attached to A and passes over a massless, frictionless pulley as shown. The smallest mass mB of block B that will start A moving when it is attached to the other end of the string is:

A.20kg

B.30kg

C.40kg

D.50kg

E.70kg

14. Block A, with a mass of 10kg, rests on a 35º incline. The coefficient of static friction is 0.40. An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top. The largest mass mB of block B, attached to the dangling end, for which A remains at rest is:

A.2.5kg

B.3.5kg

C.5.9kg

D.9.0kg

E.10.5kg

15. A block is first placed on its long side and then on its short side on the same inclined plane, as shown. The block slides down the plane on its short side but remains at rest on its long side. A possible explanation is:

A.the short side is smoother

B.the frictional force is less because the contact area is less

C.the center of gravity is higher in the second case

D.the normal force is less in the second case

E.the force of gravity is more nearly down the plane in the second case

16. A 50 kg skier is pulled up a frictionless ski slope that makes an angle of 8 degrees with the horizontal by holding onto a tow rope that moves parallel to the slope. Determine the magnitude of the force of the rope on the skier at an instant when (a) the rope is moving a constant speed of 2.0 m/s, and (b) the rope is moving with a speed of 2.0 m/s but that speed is increasing at a rate of 0.10 m/s2 .