Pushing mass up and down slopes

Science · Forces & Motion · ages 16-17

Name ______________________ Date ____________

A 2 kg crate sits on a 30 degree slope. Take g as 9.8. What is the down slope pull of its weight in N?
Answer: ______________
How does weight split on a slope of 30 degrees?
- m g sin down the slope and m g cos into it
- m g cos down the slope and m g sin into it
- Half the weight each way whatever the angle
That crate slides without friction. What is its acceleration in metres per second squared?
Answer: ______________
How do you find the friction force on a slope?
- Mu times the full weight always
- Mu times the normal force
- m g sin whatever the grip
What is the normal force on that 2 kg crate on the 30 degree slope? Give your answer in N, to the nearest whole number.
Answer: ______________
The coefficient of friction is 0.4. At what angle does sliding begin?
- 45 degrees
- About 68 degrees
- About 22 degrees
Mia says that on a steeper slope the normal force grows because the weight grows. Is Mia right?
Circle one: True False
A 2 kg crate slides down a 30 degree ramp with mu 0.2. Down pull 9.8 N, friction 3.4 N. What is its acceleration?
- 3.2 metres per second squared
- 4.9 metres per second squared
- 6.6 metres per second squared

Answer key

For grown-ups. Fold this page away before handing over the rest.

9.8 · Down slope is m g sin 30: 19.6 times 0.5 is 9.8.
m g sin down the slope and m g cos into it · Tilt swaps which trig sits where: sine pulls down, cosine presses in.
4.9 · Without friction a is g sin 30: 9.8 times 0.5 is 4.9.
Mu times the normal force · Rougher surface or harder press both raise the cap mu times N.
17 · N is m g cos 30: 19.6 times about 0.866 is about 17.0.
About 22 degrees · Sliding starts when tan theta is mu, and tan 22 degrees is about 0.4.
False · Weight is fixed and N is m g cos, which shrinks as the angle grows.
3.2 metres per second squared · Net 9.8 minus 3.4 is 6.4, and 6.4 over 2 is 3.2.