Forces and Motion
5 marks · EasyA cart is pushed along a straight path. The following data was recorded:
Write down the SI units for (i) speed and (ii) acceleration.
The cart moves a distance of 8 m in 4 s at a constant speed. Calculate its speed.
If the mass of the cart is 2 kg, what is its momentum at this speed?
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) (i) m/s (metre per second), (ii) m/s^2 (metre per second squared)
(b) 2 m/s
(c) 4 kg m/s
Common mistakes: mixing up m/s and m/s^2; forgetting units
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct unit for speed (m/s) given.
B2 (a) · 1 mark · Correct unit for acceleration (m/s^2) given.
M1 (b) · 1 mark · Speed = distance/time substitution with correct values.
A1 (b) · 1 mark · Correct evaluation: 8/4 = 2 m/s.
A2 (c) · 1 mark · Momentum calculated as 2 × 2 = 4 kg m/s.
Worked solution
a) (i) The unit for speed is metre per second (m/s).
(ii) The unit for acceleration is metre per second squared (m/s²).
b) Speed = distance ÷ time = 8 m ÷ 4 s = 2 m/s.
c) Momentum = mass × velocity = 2 kg × 2 m/s = 4 kg m/s.