Circular Motion Practice Questions X
Level : Physics I
Name :
Date :
Teacher : Kim
f =µFN
∑ Fr = mar =
Solve the following questions. Please show your work~
1. A speed skater goes around a turn with a 31m radius. The skater has a speed of 14m/s and experiences
a centripetal force of 460N. What is the mass of the skater?
(a) 82kg
(b) 73kg
(c) 64kg
(d) 55kg
2. A child is twirling a 0.012kg ball on a string in a horizontal circle whose radius is 0.1m. It travels
around the circle with a speed of 1.26m/s. (i) Determine the centripetal force on the ball. (ii) If the speed
doubles, then how much does the centripetal force increase?
(a) 0.19N, double
(b) 0.25N, doubles
(c) .25N, stays the same
(d) 0.19N, quadruples
3. A ball swings in a circle by a 12m cable attached to a vertical pole. The
mass of the ball is 220kg. Find the tension in the cable and (b) the speed of
the ball
(a) 5100N, 15.1m/s
(c) 4580N, 15.1m/s
65˚
(b) 5100N, 4.2m/s
(d) 4580N, 4.2m/s
4. At what angle should a curve of radius 150m be banked, so cars can travel safely at 25m/s without
relying on friction?
(a) 11°
(b) 16°
(c) 23°
(d) 34°
f =µFN
∑ Fr = mar =
5. A curve of radius 120m is banked at an angle of 18°. At what speed can it be negotiated under icy
conditions where friction is negligible?
(a) 43.2m/s
(b) 34.6m/s
(c) 25.3m/s
(d) 19.5m/s
6. At amusement parks, there is a popular ride where the floor of a
rotating cylindrical room falls away, leaving the backs of the riders
‘plastered’ against the wall. Suppose the radius of the room is 3.3m and
the speed of the wall is 10m/s when the floor falls away.
(i) What is the source of the centripetal force acting on the riders?
(ii) How much centripetal force acts on a 55kg rider?
(a) 1280N
(b) 1667N
(c) 1833N
(d) 2100N
(iii) What is the minimum coefficient of static friction that must exist between the rider’s back and the
wall, if the rider must remain in place when the floor drops away?
(a) 0.112
(b) 0.179
(c) 0.323
(d) 0.543
**7. A car can negotiate an unbanked curve safely at a certain maximum speed when the coefficient of
static friction between the tires and the ground is 0.88. At what angle should the same curve be banked for
the car to negotiate the curve safely at the same maximum speed without relying on friction?
(a) 41.3°
(b) 34.5°
(c) 26.4°
(d) 19.7°