SUVAT Questions
A cheetah starts from rest and
accelerates at 2.0ms-2 in a straight line for 10s.
Calculate:
The cheetah’s final velocity
Use
of v = u + at → v = 2x10
20m/s
The distance the cheetah covers in this
10s
Use
of s = ut + ½ at2 → s = ½ x 2 x 102
s
= 100m .
An athlete accelerates out of her
blocks at 5.0ms-2.
How long does it take her to run the
first 10m?
Use
of s = ut + ½ at2 → t2 = 2s/a = 20/5 = 4 2
marks
t
= 2s
What is her velocity at this point?
Use
of v2 = u2 + 2as → v2 = 2x5x10 = 100 2
marks
v
= 10m/s
A bicycle’s brakes can produce a
deceleration of 2.5ms-2. Calculate the distance travelled by the
bicycle before stopping if it is moving at 10ms-1 when the brakes
are applied?
Use
of v2 = u2 + 2as → 0 = 100 – 2 x 2.5 x s 2
marks
s
= 20m
An aircraft is at rest at one end of a
runway which is 2.2km long. The aircraft accelerates along the runway with an
acceleration of 2.5ms-2 until it reaches its take-off speed of 75ms-1.
Calculate:
The time taken to reach take-off speed
Use of v = u + at →
75 = 2.5t 2
marks
t
= 30s
The distance travelled in this time
Use of s = ut + ½ at2
→ s = ½ x 2.5 x 302 2
marks
s = 1125m
Just as the aircraft reaches take-off speed, a warning light
comes on in the cockpit. Reverse thrust can produce a deceleration of 4.0ms-2. For reasons he will have to explain at the
enquiry, it takes the pilot 2.5s to react, during which time the aircraft
continues at its take-off speed. Determine whether the aircraft can stop before
it reaches the end of the runway.
Distance travelled
before braking = 75 x 2.5 = 187.5m 4
marks
Use of
v2 = u2 + 2as → 0
= 752 – 2 x 4 x s
s = 890 m
Conclusion – yes the
runway is long enough since the distance required to stop is smaller than the
remaining length of runway (1075m).
The Eagle is landing on the Moon. Neil
uses the LEM’s engines to keep its speed of descent constant at 5.0ms-1
from the time when the craft is 14m above the Moon’s surface until it is 4.0m
above the surface. Neil then cuts the engines and lets the Eagle fall freely to
the Moon’s surface. The acceleration of free fall near to the Moon’s surface is
1.6ms-2. Ignore air resistance.
Calculate
The speed of impact
Use
of v2 = u2 + 2as → v2 = 52 + 2 x
1.6 x 4 2
marks
v
= 6.15 m/s
The time taken to travel the last 4.0m
Use of v = u + at → t = (v – u)/a = (6.15-4)/1.6 2
marks
The time taken for the full 14m
descent.
time travelling at constant velocity from s = ut + ½ at2 →
t = s/u = 10/5 = 2s
Total time = 2.72s
In a test, a car was propelled into
gravel trap at 50 ms-1. It
came to rest in a time of 0.4 s.
Calculate the
acceleration?
-125 ms-2 1
mark
Calculate the distance travelled before
it came to a halt?
Use
of s = ut + ½ at2 → s = 50x0.4 – ½ x 125 x 0.42 2
marks
Robin shoots an arrow at Guy who is
riding directly away from him. When he shoots the arrow Guy is 60 m away. When
the arrow bounces off Guy’s chainmail, he is 80 m away. If the arrow travels at
70 ms-1:
Calculate the time taken for the arrow
to hit Guy?
Use
of s = ut + ½ at2 3
marks
Realises
a = 0, s = 80 and u = 70 m/s
t
= 80/70 = 1.14s
Calculate Guy’s speed?
v
= s/t = 20/1.14 1
mark
v
= 17.5 m/s
What assumptions did you make in
solving this problem?
The speed of the arrow doesn’t change – air resistance can
be ignored. 1 mark
Phileas Fogg’s balloon is gaining
height. To avoid crashing into a mountain Passepartout tries to lighten the
load by dropping a sandbag from a height of 150m. The hot air balloon is moving
upwards with a velocity of 5.0ms-1. Ignore air resistance.
What is the initial velocity of the
sandbag?
5m/s
upwards 1
mark
How long will the bag take to reach the
ground?
t
= 6.06s
